Well, in my opinion, what makes a 'family member' is their involvement in your life. Not that you considered him your 'father', you said 'biological father', so I'm assuming there is some distance between you and him either emotionally or mentally.
Everyone needs love, and it is very compassionate/wise of you to help this man out, father or not. Buddha speaks of 'unconditional' love. Love him regardless of how he treats others, regardless of the fact that he is your biological father.
He is a human
being. All beings deserve to be loved, unconditionally. Including him.
I hope that helps. Good luck