Answer
Based on official Jordanian legal texts
After the father's death, guardianship over the minor passes according to the order set in Article 223 of the Personal Status Law: after the father comes the trustee he appointed, then the true grandfather, then the grandfather's trustee, then the court or the trustee the court appoints.
If the father appointed a chosen trustee during his life under Article 230, that trustee takes charge of the minor's affairs; otherwise, if a true grandfather exists he is guardian, and if none exists the court appoints a qualified trustee to care for the minor and his funds. The court may choose the mother if she meets the trustee's conditions in Article 231, as the closest to caring for her children.
Throughout, the trustee is subject to the court's oversight under Article 235 and submits a report every six months under Article 239, to preserve the minor's interest.
Assessing to whom trusteeship devolves and appointing the trustee remains within the Sharia Court's competence on the facts of each case.
This is a general explanation based on Jordanian Personal Status Law and does not replace advice from a qualified lawyer in a specific dispute.