How can I obtain temporary custody of my kids if their dad took them for a weekend and won't give them back? How long will it take to obtain? He sees them once every two years and is not on the birth certificate.

Am I accurately assuming that there is no a court order concerning custody and visitation? He is not on the BC but there is no question that he is in fact their biological father? If that is the case, each parent has the right to full custody.

You need to file suit for custody, of course.

Unless there is a court order that designates him as the legal father, he has no rights to hold the children. Go where is he with the police and pick up the children.