Handle particular cases in simple family tree

geneit_app/src/widgets/simple_family_tree/SimpleFamilyTree.tsx

@@ -254,6 +254,7 @@ function NodeArea(p: {
   let pers2 = p.node.spouse?.member;
   let didSwap = false;
 
+  // Show male of the left (all the time)
   if (pers2?.sex === "M") {
     let s = pers1;
     pers1 = pers2;
@@ -293,10 +294,37 @@ function NodeArea(p: {
   let childrenLinkX: number;
   let childrenLinkY: number;
 
-  if (p.node.spouse) {
+  // If the father is the father of all the children, while the
+  // mother is not the mother of any of the children
+  if (
+    pers2 &&
+    p.node.down.every(
+      (n) => n.member.father === pers1.id && n.member.mother !== pers2!.id
+    )
+  ) {
+    childrenLinkX = parent_x_offset + Math.floor(memberCardWidth(pers1) / 2);
+    childrenLinkY = p.y + CARD_HEIGHT + 2;
+  }
+  // If the mother is the mother of all the children, while the
+  // father is not the father of any of the children
+  if (
+    pers2 &&
+    p.node.down.every(
+      (n) => n.member.father !== pers1.id && n.member.mother === pers2!.id
+    )
+  ) {
+    childrenLinkX = beginSecondFaceX! + Math.floor(memberCardWidth(pers2) / 2);
+    childrenLinkY = p.y + CARD_HEIGHT + 2;
+  }
+
+  // Normal couple
+  else if (p.node.spouse) {
     childrenLinkX = Math.floor((endFirstFaceX + beginSecondFaceX!) / 2);
     childrenLinkY = middleParentFaceY;
-  } else {
+  }
+
+  // Single person
+  else {
     childrenLinkX = parent_x_offset + Math.floor(memberCardWidth(pers1) / 2);
     childrenLinkY = p.y + CARD_HEIGHT + 2;
   }