פירוש על קידושין 34:14

The above baraita implies that a non-Jew inherits from his father. That is why the baraita had to say that the son/daughter does not inherit the slave. They do inherit, just not this slave. [We should note that we do at times find rabbis legislating laws for non-Jews even though it is quite clear that non-Jews do not obey rabbinic law].

When a non-Jew converts to Judaism, he no longer inherits from his parents from biblical law. But he does inherit from them from rabbinic law. Below is proof.