Well, fighting is not just a matter of who's in the right or whether you think it's worth it or not. You also have to consider a person's capacity to fight. In a fistfight, that may mean strength of arms, in your current case, that could mean having the money and time to engage a lawyer with a reasonable chance of winning against any lawyers your relatives might hire. In any kind of case, endurance is important.
My gut reaction is that your parents are right, but this may not necessarily be correct. If the money involved is large enough (or needed badly enough), if your relatives are stupid enough, the relative will and strength of your parents. All these things could affect your scenario.
I guess I can't really say. Just don't conflate a desire for vengeance with a need to win an unwinnable fight.