So one of my Sims destroyed a marriage.
I made a family a month or so ago and put them in Hidden Springs. It contained one set of cousins and one set of brothers. There was no cousin option in Create-a-Sim, though, so they had to be listed as house mates. Anyway, here's the lowdown of the original Sims:
Amaranth--a smoozy witch with a Life-Time Wish to cure Sims affected by curses. Just recently reached the top of the Medical career. Has one son, who turned out even more orange than Donald Trump.
Lysander--the ghost of Amaranth's dead cousin. He's childish, easily impressed, and loves animals. Is now married with a ghost daughter.
Kane--Amaranth's fiance, at start of game. They're married now. He's a virtuoso and a bookworm, and is making bank playing for tips at the local theater before movies.
Meg--Kane's younger brother. The only human in a family of witches, and the unwanted sixth son of parents who just wanted to finally have a daughter, damn it! They named him Megan anyway, and he just rolled with it. He's flirty and is currently trying to work his way up the Alchemy career ladder.
I used a cheat to have all my Sims know everyone in town, which made it easier to make friends and also made it so that everyone gets asked out on like 12 dates a day. Meg accepts most of these dates. One such date was with an older fairy woman, Catarina Vanderburg, who he quickly discovered was married. That didn't stop Meg, though. He kissed and hugged the crap out of her until she was a romantic interest, but eventually ended the date after it became apparent that the other people around town didn't approve of Catarina out on a date with a younger man when she had a husband and two adult children at home.
So they courted in secret. Meg called her regularly for WooHoo, and she spent the night a few times. Eventually, they conceived a son, who Catarina named William. Shortly afterward, I hovered over her picture in Meg's relationships tab because I wanted to see what personality traits she had, and discovered that she was no longer married.
They recently tried for a baby three times in a row, and I'm 99% sure it worked the last time, so I expect to update you with the news of the child once it is confirmed.
Also, Catarina's son's live-in girlfriend has called Meg to ask him out in a date at least once. I'm not sure if I should go down that route, but she is closer in age than Catarina is, and he does have an aspiration to date five different sims, so I might....