There are certain levels you have chances of unlocking it at:
5 (For the natural born ladie's men who don't believe in cooties), 8 for those determined to be determine to be different, 10 for those people who just want to say "I have a GIRLFIREND!", 12, for the ones who just learned about the birds and the bees, 14, because, well, you know, they're 14, and do, you know, stuff, 16, for those whose relationship with a girl is actually romantic, 18, for those who met them in college, and are college-ey like that, 21, for the people who now are "ALCOHOL, ALCOHOL, ALCOHOL!", 25 for those hopeless romantics who have spawned a thousand different cheesy soap operas, 30 for more cheesy soap operas, 40+ for those divorcees who end up with a 20 something year old, and makes everybody think they're a pervert (Or "cougar", in the case of women), and then those people who are just forever alone. Hope this answered your question.