Could one say swóje córki, swói bracia?
No, swój means that the possessor is the same as the subject of the sentence, but here there is no subject so it’s not possible to use it.
I'm not sure I understand, isn't there an implied subject here? Could you give this sentence so swoje would be appropriate?
Swoje doesn't make much sense here. If you want to use it you must have a subject, for example "He loves his daughters" = "On kocha swoje córki".
why is c pronounced two different ways? ts and ch?
It's pronounced as "ć" before "i" and as "c" everywhere else.