Pretty sure the game hasn't been geared towards using more than one cock, though the above suggestion is possible, Emperor knows whether you can actually do anything with said arrangement. In fact, the same I believe is true of female genitalia.
Honestly if the game had really anything at all that was fully fleshed out, even just one thing it'd be worth playing, but too much of it is so half-assed, partially implemented, left in a broken state, or just straight up placeholder that's promised but not in yet and likely never will.