To whom is the trust delivered after the death of its unmarried owner, in light of the father disowning his son, and does the mother inherit?

You must return the deposit to your friend's heirs, as his father inherits from him by lineage, not by righteousness, unless there is an impediment to inheritance such as murder, slavery, or difference in religion. Allah Almighty has commanded the return of trusts to their rightful owners. If you fear a lack of trustworthiness from one of the heirs, gather them and hand over the deposit to them, informing them of its true nature. None of the heirs is permitted to claim sole possession of the deposit without the others. To identify the heirs and how to divide the inheritance, you can consult a Sharia (definition) court or scholars.