Mother walked out on my son and I when he was approximately 4 months old. Now my son is 4 years old and has never spoken or been around the maternal mother so the son doesn't even know who she is, he calls my sister mom because she has help raise him. This morning the biological Mother came to my sister's house with the police and took my son saying my sister had kidnapped him. Please inform me what I can do regarding getting my child back?

I'd start with getting a lawyer. I'd also be pertitioning for full custody if you haven't already. Your lawyer will know what to do and be able to draft the appropriate things in the approriate language.

Do you live with your sister? If you do live with your sister I'd also go file a copmplaint with the police proving YOU are the father and the child was improperly taken from you... if you DON'T live with your sister, but the child did... and your sister didn't have a custody order in place... you are basically screwed because a parent trumps any third party in the absence of a court ordered/approved custody order.

I assume SHE (the mother) didn't petition for and get a custody order from Family court.

[He] ... has never spoken or been around the maternal mother ...

Has he ever been around the paternal mother? ("Maternal" is redundent in that sentence; "Maternal" is an adjective meaning being a mother. All mothers are maternal. Conversely, "paternal" describes a parent who happens to be a father.)

Anyway, normally both parents share full custodial rights to their children. So when the parents are estranged (separated, divorced, or no longer "living together"), it is always a good idea to go to court and get a specific custody and visitation schedule ordered. Otherwise, you are asking for this to happen.

What is the legal status.

1 the police almost never get involved in these cases, unless there is paper work

In these four years, have you went to court and get a custody order, giving you custody of the child.

Has mother tried to contact child, and you refused?

If you have a custody order, you file an emergancy order, to make her bring the child back.

If there is no custody order n place, you hire an attorney, and file for custody, proving you raised child this entire time

I suspect, that, when the bio mother walked out, you did nothing to legally establish custody. A big mistake on your part.

I would not be concerned about your sister being prosecuted for kidnapping I doubt if charges will actually be brought. If they are, you simply testify that you had authorized your sister to care for your son.

Have you spoken to the police? Do you know where your son is now? If the mother is hiding him from you, then she is more guilty of kidnapping than your sister. So your first thing would be to talk to the police. If you have any proof that the mother had abandoned the child, you bring that to the police. You can question why the police supported the mother taking the child without proof of custody.

You should also go to court tomorrow morning to establish custody.