I wonder how companies like Y Combinator are structured. Y Combinator is a seed accelerator, investing in and consulting businesses. On Y Combinator's web site, there is a list of partners. Y Combinator is registered as an LLC.
In particular I wonder:
Consulting Corporate Structure Investors Shares Ycombinator
I don't know about Y-Combinator in particular but most investing funds are organized the same way.
Usually, there is a management company which manages a fund of money on behalf of limited partners who put in the money. The management company partners are called general partners.