User blog comment:Briceice/weird questions/@comment-1595565-20100808020154

If devil fruit abilities became genetic then everyone (and I mean EVERYONE) would have multiple devil fruit abilities, and there can only be one of each power in existence at any given time. Being able to give the abilities to offspring would totally kill that rule. The best real-life comparison would be a man getting a tattoo, conceiving a son, and the son would have the same tattoo in the same spot when he is born. It can't work.