it seems your post is similar to the other one. you do not provide enough information upon which a response can be provided. however, generally speaking aunts & uncles do not have legal standing to file for and seek custody of their neice or nephew. If you standing in loco parentis, then perhaps you can seek custody.
Under Pennsylvania law -- which may or may not apply, depending heavily on whether Pennsylvania courts have ever been involved in the custody situation, along with the circumstances of your case and the mother's present whereabouts -- it is possible that your parents (i.e., the child's grandparents), can ask a court for a share of custody; whether they would get it is another question, and also depends on the circumstances of the case. Also under Pennsylvania law, however, extended family members other than grandparents and great-grandparents have no standing under the law to sue for custody.
The best and strongest case for custody of a child is always going to be made by a parent, so much may also depend on your brother's intentions and his ability to carry them through. Given that the answer you seek is so very situation-dependent, your brother and/or your parents are best advised to consult with a lawyer to see what options are available to them in the event that you manage to locate the mother and the child.
This response is offered for informational purposes only, does not create a lawyer/client relationship, and should not be taken as legal advice.
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