First, for point 2, no matter how many advantages they got from their family, how many people would willingly cite ‘inheritance’ as their source of wealth? I’m pretty sure there exists at least one rich person who honestly admits they were lucky and maybe didn’t deserve it, but I’m not sure there’s more than one.
Second, there’s a difference between the amount of cash directly inherited upon a relative’s death, and the total amount of advantage gained from one’s family. I mean, George W Bush probably hasn’t inherited much cash in the strictest sense, but there’s little doubt that he would be much much much less wealthy if he’d had a different last name.
If you want to avoid having to decide exactly what counts as ‘inherited wealth’, you could look at what’s called ‘intergenerational mobility’, which just looks at to what extent rich people tend to be children of other rich people.