Is a guardianship legal if biological parents were not served with petition for guardianship?

Guardianship is legal when the judge says it is. An attempt must be made to serve the biological parents but if service is not possible for whatever reason an argument can be made to the judge to grant guardianship without it.

Additional: If the child was removed from the custody of the biological parents by court order due to some shortcoming or failing of the parents to 'nurture and protect' the child, and custody was awarded to a foster family, you would.should have been issued a court order to that effect. . . IF you could have been found. If the state Dept. of Children and Family Services (or whatever they call it in your state) initiated the petition for the safety of the child, you need not have been served with any formal legal papers prior to them taking this action.