At 16, I'm betting her father (your father?) is the one who is actually going to end up supporting this kid. As such, your sister has no place in stating she doesn't want the actually baby's father to financial contribute. Once your sister is paying for all medical bills, baby gear, housing, utilities, transportation, school, daycare, clothes and personal expenses totally on her own for both she and baby, then she may decide who gets to help her contribute to baby's support. If sis plans to use any welfare services to help support junior, the state will not give her a choice about making the father pay. The chance that a 16 year old is going to be able to make enough money to fully support them both without any assistance is abysmally low.