I'm in the middle of something similar except sort of on the other side, although as an individual I'm getting more than my father's four adult step-children, altogether they're getting 2/3's, me 1/3. I'm coming out more than a millionaire, but less than a multi-millionaire to be honest, so your 45K doesn't seem like much to me, but that's not my point.

It absolutely should've been split evenly. It should not have been split based on merit or love or sacrifice or any of those vagaries. Your grandparents screwed your cousins. Just like my dad screwed me by giving a large part of the family fortune, more than half of which came from my grandparents who his step-children never met. My family, me and my son are the last in the line. Those people, those step-children are not entitled to anything more than a small amount. $100,000 each maybe would've sat fine with me. But $375K each. Anyway, that's not my argument

Anyway, here's my logic, I hope, everyone is different and some people are more lovable and more loving and some are more available and some more reticent in their relationships. Say those cousins, like, me and my other grandparents on my mother's side and my father didn't see eye to eye on a lot of things, they conservative, I liberal, they critical and controlling, bigoted, hateful, not worthy of a lot of respect, so I kept my distance. But my cousin and my father's step-children didn't see it that way, they lived with them, loved them as parents, somehow were close to these people, my grandparents, this person, my father, who to me were cold, uncaring, maybe knew some things but had a lot of faults. Inheritance should be fair, it shouldn't be a reward for good behavior, or as some people who don't see eye to eye with their elders, ass kissing. That's how I see my cousin, how I see my step-nothings. All they did is kiss ass to get what they got and I don't know if they deserve it or not but I have more respect for myself than to ever have been like that. I played nice toward the end and got a good share from my father which made up for being totally excluded from my grandparents' will (I wasn't even mentioned in the obit), but I never compromised or lied or hurt anyone. They fucked me in the end.

45K isn't much to build a life on. But like lotto winners who find they are surrounded by desperate family and have to make a choice so do you. It isn't family, it's fairness. You should split it like your grandmother should've split it if she was being fair and kind and loving and forgiving and understanding. They might not have been as close as you but they were family, just like you.