This achievement will unlock when you play Blackjack with your girlfriend/wife. It unlocks as soon as the game is loaded. When it actually occurs is most likely random as I've hit it twice so far, once in December and then again in July.
When you actually play, you pick the number of wins to play to (3/5/10), and then you both get dealt your hands. The first option is 'hit' and the bottom is 'stay'.