I see! It's a transfer between generations, though not an inheritance (which some people suggest to tax heavily).
Again, Bezos got about $300k from his family (both his parents were doctors), which, I think, is far below the level of "unjust inherited fortune" or what is usually people suggest to tax into oblivion.
Yes, when your parents help you, it's helpful — it's nearly tautologically true. This is why I as a parent do help my grown-up son sometimes. Limiting this behavior is not quite realistic, and would be met with a huge backlash (justly, to my mind).
The problem is not intergenerational help, that existed at least as much if not more in times of less inequality. The problem is the size of the spoils. Intergenerational help is only brought up as a counter to the tired "it's your fault if you aren't a billionaire" defense (which is rarely brought up by billionaires themselves but all the time by their broke admirers)
(Note: I'm not saying the funding from parents was sufficient, or even necessary in Bezos' case.)