One of my younger siblings was getting married and it was noted that their future mother in law was the same age as our oldest brother. Both of them were still young enough to have children so it started people wondering that if they got married and had a child, how would that child be related to the rest of us? It’s my sister in laws mother, who’s theoretically marrying my brother. So the child is related by blood and by marriage right? Plus this would be my parent’s grandchild and sort of grandchild to my brother’s new spouse, no that’s wrong, I think? What if they had got drunk at the reception and then just got together and had a kid? This line of thought is making my head hurt!