Well, there is one problem with generational curses - they are a bit difficult to...let's say program accurately.

The first few generations - three is the usual number, though I've known cases that go up to seven - it works as intended. Only the target suffers.

But after that, things deteriorate a bit. Like in this case, becomes unpredictable. Brings in collateral damage.

Of course, by the time that stage is reached, most curses just deteriorate too far to have any effect. OP's ancestor must have pissed off someone seriously powerful - or something immortal - if the curse is still effective even now.

And the vegan thing... Don't know about OP, but such curses often have clauses that will shut out such escape routes. Maybe a craving for meat, or health issues that require a non vegetarian diet...