Q: Half sibling situation?

A: First, the answer is arguably yes, in that a petition for sibling visitation is possible. That said, the more important question is: in what way is the mother dictating to your husband who he can bring those children around? Even if the mother has sole custody - and unless their agreement/order says otherwise - she cannot dictate to your husband the structure of his visitation. Thus, you should call a Bronx Family Law attorney to schedule a consult for a full assessment.