Most commonfolk throughout much of history had very meager lodgings, and most families would sleep together both for warmth as well as the simple fact that they didn't have the space for people to sleep separately. If mom and dad were in the mood to procreate, the rest of the family was just... there.
Considering the amount of stuff I know to be BS, that I have found in IZI to date, I have a hard time believing any of this