My main sim that I created in CAS was a serial romantic who had 9 kids by 5 different fathers (lots of twins were involved). In Sims 2, I might have felt bad because romance sims hated being married or having children. But in Sims 4, because I never gave her the hates children trait, she was perfectly happy to be a serial mother as well as a serial dater. It actually started with fulfilling one of her whims, actually. And I have had all of the children retain relationships with their non-custodial parent, so I don't think anyone in the family suffers. The only time I ever felt guilty was when one of the fathers became very sad upon seeing her flirt with another man. The angry responses didn't bother me but I hated making them sad. And the youngest two are the children of Father Winter, of which my neighborhood has two, and when I finally played that household at Winterfest again when they were teens the other one showed up, so they have never met their father. But mostly, regardless of how their lives line up with traditional values, most of my sims are pretty happy most of the time. So no guilt.