What will happen is Eddie will reveal that Rey has problems getting an erection and therefore Rey and his wife didn't know what to do. Wanting a child really bad, Rey turned to Eddie in order for that to happen. Eddie and Rey's wife start going at it while Rey watches. Suddenly, Rey magically gets an erection and decides to join in. They double team but then can't figure out who the child is. The main gist of the secret is that Rey was in her anus but Eddie was in the right hole therefore Dominic is Eddie's son. The plot thickens when Rey Mysterio, now amazed at the power of his erection, has sex with Eddies wife and it's revealed that BOTH of the little girls are in fact Rey's.
EDIT: I just realized that made absolutely no sense at all. Oh well, it's still morbid and disturbing.