I thought at the beginning, Jordan says he came from a family of both his parents being accountants, however later it appears that Jordan's Father is an ex-Cop and a PI?
Belfort's father Max, was to "Maintain order" in the chaos they had going at the firm. It was a free-for-all, with sex/drugs/money/testosterone going full steam. Think Sodom and Gomorrah, and Max was the cop trying to keep things from getting too far out of hand, more like a way to keep them connected to the rest of the world. Remember the scene where they discuss EJ entertainment? He had to try to keep everyone balanced out.