As heads as of a monarchial state they are the direct owners of Saudi state property and enterprises. Saudi Aramco alone has an estimated value of several trillion dollars, and were its value to be liquidated, that cash would be transferred into their private Coffers.

If they liquidated the company, the money would not go to just a few people.

https://en.wikipedia.org/wiki/House_of_Saud

The family in total is estimated to comprise some 15,000 members; however, the majority of power, influence and wealth is possessed by a group of about 2,000 of them. Some estimates of the royal family's wealth measure their net worth at $1.4 trillion, this figure includes the market capitalization of Saudi Aramco the state oil & gas company and its vast assets in fossil fuel reserves.

If you spread that money across 2,000 people, it's $700 million each.

If you spread it across 15,000 people, it's about $93 million each.

https://en.wikipedia.org/wiki/Mars_family

The Mars Family, by comparison, only has a few people (maybe a dozen or two). Even spreading $126 billion across 24 people means that their average net worth is something like $5 billion each.