Malcolm Landgraab disappeared from family tree

I don't know if this is a bug or not... but Malcolm Landgraab seems to have disappeared from my game. Even his tombstone no longer says RIP like Geoffrey's does? Now that he's no longer in the Landgraab family tree, his children don't show up anymore, either. However, when I open the relationship panels between Geoffrey and Malcolm's children, they still show the relationship of grandfather/grandchildren. But now that Malcolm is no longer connecting his children to the rest of the family, Malcolm's grandchildren no longer show up as related to the rest of the Landgraabs.