A pawn may "forget" their direct relative too.
White Shrew was a raider. He was captured and recruited. He seemed to be single but one beautiful day his wife came with a raid. She just appeared on his Social tab out of nowhere, and he seemed to like her. She was killed, sadly, and cremated. Shrew was supposed to mourn her for 30 days. 13 days passed... Load the
saved game and skip about 2 in-game hours. Shrew not only forgets that she died, he forgets that she has ever existed (mood debuff vanishes just as the Social tab record). Only one thing left he cannot explain, hate to Kadence 'Kay' Sherrill. Killed my spouse: -65.
Sad story.
I believe, some future raid may come with his wife. Again.
So, the bug is: [1.3.3117 + Royalty] the game makes up relatives on the go, and it may delete them. It would be better to fix relatives when a character is created.