During a divorce proceeding, what happens the couple's children who are old enough to express which parent they'd like to live with and also express that they prefer to be separated from their siblings?

Where custody, care & control decisions are concerned, in the absence of agreement between parties, the Court has to make a decision with the welfare of the children in mind, based on the evidence made available in the affidavits (i.e. parties' accounts, counselling reports etc.) If the children are old enough to express an opinion, their opinion about living separately from their siblings should also be taken into account.