Do I inherit in my husband's house, which his father registered in his name, knowing that he is his only son, and that his father built it with his own money?

If the father truly bestows the house upon his son as a genuine gift, and the son takes possession of it, then it becomes his property, which his heirs—including his wife—will inherit. However, merely writing the house in the son's name without actual ownership transfer and possession does not complete the gift. It is advisable to refer the matter to the Sharia (definition) court to examine the circumstances.