That would explain my family. Case in point:
We all went back home for the holiday weekend. After a bottle (or two) of wine and some plumbing issues, MS declared she was ovulating. Yep. This led to ma making an exception to the rule of "No sex at ma and pa's" for the evening. This led to me writing up a babysitting agreement between ma and MS. I signed as the witness.
If only I had a copy of that agreement to post...
I have yet to hear if she took.