Can Retro Active support be ordered against a father never married to the mother, not listed on the child's birth certificate as the father, never allowed to speak to, see, or participate in the child's life for the 5 years he has been alive because the maternal grandmother of the child would stop babysitting for the child if her daughter allows visitation with the man she claims is the child's father.Grandma's threats thus creating a hardship for herself and her son.

Is there a current support order from the courts and a visitation order?

Threats of grandmother have nothing to do with court orders,

The father could always see child, if he had gotten a child visitation order from the court and had forced it to be enforced. So fathers claim has no merit that he could not see child, unless the mother refused to obey a court ordered visits.

Retro support can be given in some US states, but not others, in general was there ever a support order though Child support enforcement or though the courts ? If so, it will go back to that date.

If not, a new filing for support the location and all events will have to be fought out in court according to state laws.