Are accents hereditary

No. Back when linguistics was really first getting its start in the 19th century, there were some theories along these lines. Grimm's Law, for example, where voiceless stops became fricatives, was once believed to have been caused by Germans being out of breath from running up and down the mountains all the time. Alternately, it could have been caused by a tendency towards earwax buildup which made it difficult for them to hear, which would be a possible genetic factor.

Although Grimm's Law is in and of itself not an accent, phonological changes over time do help to differentiate accents from one another. However, there are other theories for why one group of people speaks one way and one another. The truth of the matter is linguists aren't entirely sure.

What is known is that your dialect is impacted by a large number of factors. Your parents' dialect(s), the region you live in/grew up in, your friends' dialects, et cetera. Genetics do not play a role.