I see two arguments here:

1. Billionaires existing is a symptom of a larger problem
2. Someone having a better start than you makes them a "nepo baby"

For the first, I and Warren Buffett somewhat agree, and I'll quote him here:

"I continue to believe that the tax code should be changed substantially," wrote Buffett. "I hope that the earned-income tax credit is increased substantially and additionally believe that huge dynastic wealth is not desirable for our society."

"Perhaps annual payout requirements should be increased for foundations," he added. "Some time ago, I testified before Senator Baucus in favor of increasing and tightening estate taxes."

...

"I believe the money will be of more use to society if disbursed philanthropically than if it is used to slightly reduce an ever-increasing U.S. debt," wrote Buffett.

That said, I likely disagree with his specific solutions, though I haven't bothered researching to figure out what those are, because he's clearly not particularly interested in crafting policy.

For the second, I largely hold to this definition of nepotism:

favoritism (as in appointment to a job) based on kinship

Someone giving their kids the best education they can isn't nepotism, that's normal parenting.

Someone giving their child an job they're not qualified for absolutely is. If you want to see examples of that, look no further than Trump and his kids.

When I look at the top billionaires, most of them are largely self-made. For example:

• Elon Musk - dropped out of college and co-founded zip2, largely with money from investors
• Bill Gates - dropped out of college and founded Microsoft, which was pretty much bootstrapped
• Jeff Bezos - graduated from college, worked his way up in his career, then started Amazon when the internet was getting big (parents did invest $300k)

I don't really consider any of them to be "nepo babies" because their parents didn't give them an undeserved job or anything like that. And honestly, none of their parents were particularly rich, except maybe Musks. Each of them had incredible luck and capitalized on the early days of consumer computing, but that doesn't cheapen the work they put in.

Do they deserve hundreds of billions? Probably not. But I don't think they really benefited from nepotism like Trump's kids, Kim Kardashian, and others did. There's a huge difference between someone who had a good start and builds something great through their hard work and someone who is handed a pile of cash or a prominent position and rides that.

If you show evidence that their success is largely dependent on their parents, I'll believe you. But if they largely built their wealth themselves, that's a harder sell. I think each of those I mentioned earned their wealth, I just think our tax system dramatically increases wealth accumulation past a certain amount, and that's what needs to be changed here.