i am/was a twin. it's weird to conceptualize for me. her name was amanda and she's still half of my soul. so there's that.
SOLAS probably doesn't have siblings
i don't like inserting headcanons that have no support. giving him siblings has ZERO support, you can't even insinuate it from what he's said
and i feel like headcanoning him siblings would just give him more man pain and who wants that