You ever stop to think that your significant other is basically just a manifestation of what makes you horny. Mom, dad...meet Jessica, she has big ol boobies, well...because I always liked jerkin it to big boobies, so figured real life big ol boobies would be even better.
Similarly, when you've been trying to have a baby and you announce it...you're basically just bragging about having unprotected sex. Still not quite sure how to run that one by my father in law...like, what can I say, your daughter is a good lay??? Like mother like daughter???...no that's worse.