his mother live in a different house away from us and i am not biologically the child's parent but he lives with me
Under appropriate circumstances you may be able to claim the child on your tax returns. However, the correct answer will depend on a very detailed review of all the facts and circumstances of your situation so there is almost no way anyone here can give you a correct answer that you can rely on without consulting with a competent local tax professional.
Please do not attempt this on your own. I would strongly urge you to at least consult with a competent local tax return preparer (preferably a CPA or accountant) to get proper advice about whether or not you can claim this child on your tax returns. Please do not just rely on answers you get for free online from people whom you've never met and whom you haven't retained to advise you. In other words, don't take candy from strangers.
My answer does not constitute legal advice and may not be relied upon by anyone for any purpose and does not constitute an attorney/client relationship or an offer to form such a relationship. This disclaimer is intended to be fully compliant with the requirements of Treasury Department Circular 230 and the terms thereof are fully incorporated by reference. If you wish to consult with me please contact me at dwatchley@newyorktaxcounsel or visit my website at www.newyorktaxcounsel.com
As Dana points out, you may be able to claim the child under the right circumstances. The following IRS link may be helpful.
Evan A. Nielsen is licensed to practice law in California. The information provided here is for educational purposes only and is not intended as legal advice for a particular matter. This response does not create any attorney-client relationship with the author. For specific advice about your particular situation, please consult an attorney.