His family's loaded, but he has 5 or so siblings (and if his family is like most development money in Forest Hill, the money is generally from the Grandfather and is spread amongst cousins). I don't think Stuart Hyman is worth about 500m. I grew up in the area around Hyman, and I know even more successful families in the same field. I think you are underestimating what Spezza has made in his career. Spezza has made 89m USD prior to agent fees, escrow, and taxes. He has likely banked around 45m to 50m USD.
Plus, family money is family money until you actually inherit it.