Question: We have only proven that a son inherits a father. What about a father inheriting his son?

Answer: If a son who only comes from the power of the father, he inherits his father; the father, whose son only has power on account of him, should certainly inherit his son.

Support: The pasuk states (Bamidbar 27:11), "(you shall give his inheritance to his relative) who is closest (to him of his family)" - the closer relative has priority - so since the son inherits his father because he is the closest relative, so too the father should inherit the son for the same reason.