diff --git a/poincare/include/poincare/allocation_failed_layout_node.h b/poincare/include/poincare/allocation_failed_layout_node.h
index b1a6c0eab..5d69dc95e 100644
--- a/poincare/include/poincare/allocation_failed_layout_node.h
+++ b/poincare/include/poincare/allocation_failed_layout_node.h
@@ -22,7 +22,6 @@ public:
   // TreeNode
   size_t size() const override { return sizeof(AllocationFailedLayoutNode); }
   const char * description() const override { return "Allocation Failed";  }
-  int numberOfChildren() const override { return 0; }
   bool isAllocationFailure() const override { return true; }
 
 protected:
diff --git a/poincare/include/poincare/binomial_coefficient_layout_node.h b/poincare/include/poincare/binomial_coefficient_layout_node.h
index 5bc521fdf..8a878c446 100644
--- a/poincare/include/poincare/binomial_coefficient_layout_node.h
+++ b/poincare/include/poincare/binomial_coefficient_layout_node.h
@@ -22,7 +22,6 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(BinomialCoefficientLayoutNode); }
-  int numberOfChildren() const override { return 2; }
 #if TREE_LOG
   const char * description() const override {
     return "BinomialCoefficientLayout";
diff --git a/poincare/include/poincare/bracket_layout_node.h b/poincare/include/poincare/bracket_layout_node.h
index 3b3272524..f8a032062 100644
--- a/poincare/include/poincare/bracket_layout_node.h
+++ b/poincare/include/poincare/bracket_layout_node.h
@@ -22,7 +22,6 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(BracketLayoutNode); }
-  int numberOfChildren() const override { return 0; }
 #if TREE_LOG
   const char * description() const override { return "BracketLayout"; }
 #endif
diff --git a/poincare/include/poincare/bracket_pair_layout_node.h b/poincare/include/poincare/bracket_pair_layout_node.h
index 851851e13..c5b1a04f0 100644
--- a/poincare/include/poincare/bracket_pair_layout_node.h
+++ b/poincare/include/poincare/bracket_pair_layout_node.h
@@ -24,7 +24,6 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(BracketPairLayoutNode); }
-  int numberOfChildren() const override { return 1; }
 #if TREE_LOG
   const char * description() const override { return "BracketPairLayout"; }
 #endif
diff --git a/poincare/include/poincare/char_layout_node.h b/poincare/include/poincare/char_layout_node.h
index bd331370e..8c5751d05 100644
--- a/poincare/include/poincare/char_layout_node.h
+++ b/poincare/include/poincare/char_layout_node.h
@@ -28,7 +28,6 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(CharLayoutNode); }
-  int numberOfChildren() const override { return 0; }
 #if TREE_LOG
   const char * description() const override {
     static char Description[] = "Char a";
diff --git a/poincare/include/poincare/condensed_sum_layout_node.h b/poincare/include/poincare/condensed_sum_layout_node.h
index 2cd0980f2..5798caa33 100644
--- a/poincare/include/poincare/condensed_sum_layout_node.h
+++ b/poincare/include/poincare/condensed_sum_layout_node.h
@@ -27,7 +27,6 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(CondensedSumLayoutNode); }
-  int numberOfChildren() const override { return 3; }
 #if TREE_LOG
   const char * description() const override {
     return "CondensedSumLayout";
diff --git a/poincare/include/poincare/conjugate_layout_node.h b/poincare/include/poincare/conjugate_layout_node.h
index 4ffd7d043..0c4ab786c 100644
--- a/poincare/include/poincare/conjugate_layout_node.h
+++ b/poincare/include/poincare/conjugate_layout_node.h
@@ -19,7 +19,6 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(ConjugateLayoutNode); }
-  int numberOfChildren() const override { return 1; }
 #if TREE_LOG
   const char * description() const override {
     return "ConjugateLayout";
diff --git a/poincare/include/poincare/empty_layout_node.h b/poincare/include/poincare/empty_layout_node.h
index 5322af1b2..ed7e36b98 100644
--- a/poincare/include/poincare/empty_layout_node.h
+++ b/poincare/include/poincare/empty_layout_node.h
@@ -39,7 +39,6 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(EmptyLayoutNode); }
-  int numberOfChildren() const override { return 0; }
 #if TREE_LOG
   const char * description() const override { return "Empty"; }
 #endif
diff --git a/poincare/include/poincare/fraction_layout_node.h b/poincare/include/poincare/fraction_layout_node.h
index cd1be1a5d..5fdf40cd4 100644
--- a/poincare/include/poincare/fraction_layout_node.h
+++ b/poincare/include/poincare/fraction_layout_node.h
@@ -33,7 +33,6 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(FractionLayoutNode); }
-  int numberOfChildren() const override { return 2; }
 #if TREE_LOG
   const char * description() const override {
     return "FractionLayout";
diff --git a/poincare/include/poincare/grid_layout_node.h b/poincare/include/poincare/grid_layout_node.h
index 9efce6c3c..15900d1e6 100644
--- a/poincare/include/poincare/grid_layout_node.h
+++ b/poincare/include/poincare/grid_layout_node.h
@@ -17,7 +17,6 @@ class GridLayoutNode : public LayoutNode {
 public:
   GridLayoutNode() :
     LayoutNode(),
-    m_numberOfChildren(0),
     m_numberOfRows(0),
     m_numberOfColumns(0)
   {}
@@ -40,20 +39,8 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(GridLayoutNode); }
-  int numberOfChildren() const override { return m_numberOfChildren; }
-  void incrementNumberOfChildren(int increment = 1) override {
-    assert(increment >= 0);
-    m_numberOfChildren += increment;
-  }
-  void decrementNumberOfChildren(int decrement = 1) override {
-    m_numberOfChildren -= decrement;
-    if (m_numberOfChildren < 0) {
-      m_numberOfChildren = 0;
-    }
-  }
-
   void eraseNumberOfChildren() override {
-    m_numberOfChildren = 0;
+    LayoutNode::eraseNumberOfChildren();
     m_numberOfRows = 0;
     m_numberOfColumns = 0;
   }
@@ -76,7 +63,6 @@ protected:
   int rowAtChildIndex(int index) const;
   int columnAtChildIndex(int index) const;
   int indexAtRowColumn(int rowIndex, int columnIndex) const;
-  int m_numberOfChildren;
   int m_numberOfRows;
   int m_numberOfColumns;
 
diff --git a/poincare/include/poincare/horizontal_layout_node.h b/poincare/include/poincare/horizontal_layout_node.h
index 6082dc5a0..6e56874c3 100644
--- a/poincare/include/poincare/horizontal_layout_node.h
+++ b/poincare/include/poincare/horizontal_layout_node.h
@@ -14,10 +14,7 @@ class HorizontalLayoutNode : public LayoutNode {
   template <typename T>
   friend class LayoutReference;
 public:
-  HorizontalLayoutNode() :
-    LayoutNode(),
-    m_numberOfChildren(0)
-  {}
+  using LayoutNode::LayoutNode;
 
   // LayoutNode
   void moveCursorLeft(LayoutCursor * cursor, bool * shouldRecomputeLayout) override;
@@ -27,18 +24,11 @@ public:
   int writeTextInBuffer(char * buffer, int bufferSize, PrintFloat::Mode floatDisplayMode, int numberOfSignificantDigits) const override;
 
   bool isHorizontal() const override { return true; }
-  bool isEmpty() const override { return m_numberOfChildren == 1 && const_cast<HorizontalLayoutNode *>(this)->childAtIndex(0)->isEmpty(); }
-  bool isCollapsable(int * numberOfOpenParenthesis, bool goingLeft) const override { return m_numberOfChildren != 0; }
+  bool isEmpty() const override { return numberOfChildren() == 1 && const_cast<HorizontalLayoutNode *>(this)->childAtIndex(0)->isEmpty(); }
+  bool isCollapsable(int * numberOfOpenParenthesis, bool goingLeft) const override { return numberOfChildren() != 0; }
 
   // TreeNode
   size_t size() const override { return sizeof(HorizontalLayoutNode); }
-  int numberOfChildren() const override { return m_numberOfChildren; }
-  void incrementNumberOfChildren(int increment = 1) override { m_numberOfChildren+= increment; }
-  void decrementNumberOfChildren(int decrement = 1) override {
-    assert(m_numberOfChildren >= decrement);
-    m_numberOfChildren-= decrement;
-  }
-  void eraseNumberOfChildren() override { m_numberOfChildren = 0; }
 #if TREE_LOG
   const char * description() const override {
     return "Horizontal Layout";
@@ -58,7 +48,6 @@ private:
   void didRemoveChildAtIndex(int index, LayoutCursor * cursor, bool force) override;
   bool willReplaceChild(LayoutNode * oldChild, LayoutNode * newChild, LayoutCursor * cursor, bool force) override;
   void render(KDContext * ctx, KDPoint p, KDColor expressionColor, KDColor backgroundColor) override {}
-  int m_numberOfChildren;
 };
 
 class HorizontalLayoutRef : public LayoutReference<HorizontalLayoutNode> {
diff --git a/poincare/include/poincare/integral_layout_node.h b/poincare/include/poincare/integral_layout_node.h
index a5cc08af5..361988c89 100644
--- a/poincare/include/poincare/integral_layout_node.h
+++ b/poincare/include/poincare/integral_layout_node.h
@@ -29,7 +29,6 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(IntegralLayoutNode); }
-  int numberOfChildren() const override { return 3; }
 #if TREE_LOG
   const char * description() const override {
     return "IntegralLayout";
diff --git a/poincare/include/poincare/nth_root_layout_node.h b/poincare/include/poincare/nth_root_layout_node.h
index 1a1ad596b..60cfde3db 100644
--- a/poincare/include/poincare/nth_root_layout_node.h
+++ b/poincare/include/poincare/nth_root_layout_node.h
@@ -12,10 +12,7 @@ public:
   constexpr static KDCoordinate k_leftRadixHeight = 8;
   constexpr static KDCoordinate k_leftRadixWidth = 5;
 
-  NthRootLayoutNode() :
-    LayoutNode(),
-    m_numberOfChildren(0)
-  {}
+  using LayoutNode::LayoutNode;
 
   // LayoutNode
   void moveCursorLeft(LayoutCursor * cursor, bool * shouldRecomputeLayout) override;
@@ -28,16 +25,7 @@ public:
   bool hasUpperLeftIndex() const override { return numberOfChildren() > 1; }
 
   // TreeNode
-  void incrementNumberOfChildren(int increment = 1) override {
-    assert(increment == 1);
-    m_numberOfChildren+= increment;
-  }
-  void decrementNumberOfChildren(int decrement = 1) override {
-    assert(m_numberOfChildren >= decrement);
-    m_numberOfChildren-= decrement;
-  }
   size_t size() const override { return sizeof(NthRootLayoutNode); }
-  int numberOfChildren() const override { return m_numberOfChildren; }
 #if TREE_LOG
   const char * description() const override {
     return "NthRootLayout";
@@ -60,7 +48,6 @@ private:
   void render(KDContext * ctx, KDPoint p, KDColor expressionColor, KDColor backgroundColor) override;
   LayoutNode * radicandLayout() { return childAtIndex(0);}
   LayoutNode * indexLayout() { return numberOfChildren() > 1 ? childAtIndex(1) : nullptr; }
-  int m_numberOfChildren;
 };
 
 class NthRootLayoutRef : public LayoutReference<NthRootLayoutNode> {
diff --git a/poincare/include/poincare/sequence_layout_node.h b/poincare/include/poincare/sequence_layout_node.h
index 85d06b9ec..63fb24d13 100644
--- a/poincare/include/poincare/sequence_layout_node.h
+++ b/poincare/include/poincare/sequence_layout_node.h
@@ -28,7 +28,6 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(SequenceLayoutNode); }
-  int numberOfChildren() const override { return 3; }
 #if TREE_LOG
   const char * description() const override {
     return "Sequence Layout";
diff --git a/poincare/include/poincare/tree_node.h b/poincare/include/poincare/tree_node.h
index 8b305fdb7..9574e7d15 100644
--- a/poincare/include/poincare/tree_node.h
+++ b/poincare/include/poincare/tree_node.h
@@ -56,10 +56,12 @@ public:
   // Hierarchy
   TreeNode * parentTree() const;
   TreeNode * rootTree();
-  virtual int numberOfChildren() const = 0;
-  virtual void incrementNumberOfChildren(int increment = 1) {} // Do no put an assert(false), we need this method for instance in GridLayout::removeRow
-  virtual void decrementNumberOfChildren(int decrement = 1) {} // Do no put an assert(false), we need this method for instance in GridLayout::removeRow
-  virtual void eraseNumberOfChildren() {} //TODO Put an assert false //TODO what if somebody i stealing a unary tree's only child ?
+  int numberOfChildren() const { return m_numberOfChildren; }
+  void incrementNumberOfChildren(int increment = 1) { m_numberOfChildren += increment; }
+  void decrementNumberOfChildren(int decrement = 1) {
+    m_numberOfChildren = m_numberOfChildren > decrement ? m_numberOfChildren - decrement : 0;
+  }
+  virtual void eraseNumberOfChildren() { m_numberOfChildren = 0; }
   int numberOfDescendants(bool includeSelf) const;
   TreeNode * childTreeAtIndex(int i) const;
   int indexOfChildByIdentifier(int childID) const;
@@ -176,6 +178,7 @@ protected:
 private:
   int m_identifier;
   int m_referenceCounter;
+  int m_numberOfChildren;
 };
 
 }
diff --git a/poincare/include/poincare/vertical_offset_layout_node.h b/poincare/include/poincare/vertical_offset_layout_node.h
index e4def7bbe..4eb5b0f94 100644
--- a/poincare/include/poincare/vertical_offset_layout_node.h
+++ b/poincare/include/poincare/vertical_offset_layout_node.h
@@ -35,7 +35,6 @@ public:
 
   // TreeNode
   size_t size() const override { return sizeof(VerticalOffsetLayoutNode); }
-  int numberOfChildren() const override { return 1; }
 #if TREE_LOG
   const char * description() const override {
     return m_type == Type::Subscript ? "Subscript" : "Superscript";
diff --git a/poincare/src/horizontal_layout_node.cpp b/poincare/src/horizontal_layout_node.cpp
index 08e69912a..5e0ed494d 100644
--- a/poincare/src/horizontal_layout_node.cpp
+++ b/poincare/src/horizontal_layout_node.cpp
@@ -217,7 +217,7 @@ KDPoint HorizontalLayoutNode::positionOfChild(LayoutNode * l) {
 // Private
 
 bool HorizontalLayoutNode::willAddChildAtIndex(LayoutNode * l, int * index, LayoutCursor * cursor) {
-  if (m_numberOfChildren > 0) {
+  if (numberOfChildren() > 0) {
     *index = HorizontalLayoutRef(this).removeEmptyChildBeforeInsertionAtIndex(*index, !childAtIndex(0)->mustHaveLeftSibling(), cursor);
 
   }