I've just realized something: The Beifongs seem to have a notorious history of well, falling out with one another. Toph fell out with her parents because of the way they treated her. Lin fell out with Toph because she never knew her father, not to mention how distant she was with Suyin due to her criminal history, and those things have plagued her ever since.
Then there's Baatar Jr. He betrayed his own family by joining Kuvira and now he spits on them. He imprisoned them for refusing to follow Kuvira. Ironically, now Jr. recieves karma by being captured himself, and face to face with his family so that makes them even. But still, for Suyin, it's much harder for her--the way Jr. said "Kuvira's my family now!", it's almost like he's dead to his family.