Every broker has its own internal rules about where to direct its order flow. Some "internalize" the trade and don't send it anywhere. Others get paid to direct the order to a specific market maker, exchange, or dark pool (called PFOF).

Others allow their clients to direct orders using a specific trading strategy. If you have a family office it's very likely this is part of the strategy.

However, ordinary retail investors are sometimes locked out of this system. I don't know Etrade's policy in particular, so I can't say for sure what you would have to do.