Eddie is in the Navy and married unhappily. For the sake of his children (3), he's sticking it out in his marriage. To keep himself sane, he steps outside his marriage occasionally, to assuage his active libido. Since he refuses to engage a hooker, he tries to develop fleeting relationships with non-professional women, but those who appreciate his sexual acumen. These trysts occur at different places around the world.
Incest to beat all incest. Brother and sister have been getting it on between each other for years because they could not find anyone who could satisfy them better than the love they had for each other. The sister had been divorced because her husband wanted a younger girl, so the brother moves in with his sister who had three kids, since he was helping pay some of the bills anyway.