The Paramour Achievement
Make love 25 times, or see another Hero do so.
Simply grab a woman (your wife, someone who looooooves you, not a prostitute) and use the Come Back to My Place expression on them. Once they are following, take them to a bed and select to have relations of the sexual kind. Unprotected/protected ... whatever floats your boat.
For the location of the Come Back to My Place expression, see the Expressionist achievement for the location of the "Come Hither Dear" book.
Reminder - Not a prostitute. It's "love", and not "sex".