Can the state collect for aid received 15 yrs ago

by Jeana
(Green Ridge, MO. USA)

My son is 19yrs old. I received aid from the state of MO. until he was three to four years old. The father was listed by me as deceased on state forms and as unknown on his birth certificate as I believed the father of my son to be a boyfriend's who had died before his birth. I recently learned I may have been mistaken as to the paternity. If the true father acknowledges paternity will they require repayment? I don't feel he should owe anything as I originally told him the child wasn't his when he asked and only recently informed him of my new suspicions.