This is part of the same bug, so I'll add it here: the overlapping of generations in the same "level" of the tree is causing visual discrepancies of sims being "married" to the wrong person:
If you hover over the sim, as above, you can see they're still connected to the right spouse. The family ties aren't broken, the glitch seems to be only visual, as the placement of sims seems to be overlapping when two sims ocuppy the same "tile" on the tree:
I have this problem as well. I even have a pair of childless sim couple suddenly having kids under them in the family tree. like registered as their child under the family tree even though the couple still doesnt have any kids yet
