Two gentlemen become Wiener Twins when they engage in lovemaking with one female partner at the same time, in a spitroast or other position.
The gentlemen in question also become Wiener Brothers, but to a greater degree and with a far more powerful bond than your average pair of Wiener Brothers.
While not exactly at the same time, a Houdini 2 or houdini cheesecake both count.
Jay: hey Jeeves, guess what!
Jeeves: uhh, what?
Jay: me & Aaron spitroasted Barbara last night!
Aaron: WIENER TWINS!!!!!!!!!!!!1