A couple of things that your question suggest are that your husband and the mother of the child were married and that you and your husband are together. If those two things are true, then your husband has the right to custody of his child at the time of the death of the custodial parent, under the law. If he and the child's mother were married to each other and she got custody, when she passed away, generally he has the right to custody. If they were not married to each other, he will have to establish that he has a right to custody and legitimate the child which is rather complicated without the mother being deceased and even more complicated if she is deceased. The Uncle who has the child has no legal rights to the child, but the father may have to file an action in court, a habeas corpus, to regain custody of the child.
If you can't tell, you really need an attorney to handle this, and our office handles these sorts of cases routinely. Please feel free to contact our office. I hope that this is helpful for resolving your legal matter.
This information is of a general nature and is not intended to be relied upon as legal advise. You are encouraged to contact and discuss your matter with an experienced attorney to more specifically address your legal needs.