Can I give my fiance legal guardianship of my son whom I have with some one else with out bio dads concent?

I have a 6 year old son. His bio father only pays child support he does not visit or take the child at all. my son and I live in a different state and with my fiance whom I have 2 other children with. all have insurance except my 6 year old son. my question is do I need the consent of my 6 year old father to give legal guardianship to my fiance.