If I remember correctly, Frodo is Bilbo's favourite nephew and not his son. He was adopted by him and made his heir. This naturally made the inhabitants west of the Branduin suspicious, as the Bucklanders even sail on the water ;D ... sus

Is there a game mechanic reason why Frodo has to be Bilbo's son? Adoption is basically possible, isn't it? ... Anyway, it's just a small detail, but if there are going to be adjustments, then it might be worth considering giving Frodo a Buckland culture. That way the Sackvilles can get all worked up ;)