I voted this because most of my Sims end up meeting 'the one' eventually: If my Sims have exes, though, they have 3 at most. The Sim they end up marrying is either a high school sweetheart, or a Sim I specifically made to be their soulmate. And usually, that soulmate is a first love: If I really like playing them as a couple, then they get to have children. For the record: I do play on infinite lifespan, so nobody ages up until I feel like it. And I often bring really beloved Sims of mine back as ghosts, bonus points if they died as an Elder and have the Knitting skill. Nobody in the household knows how that sweater got there, but they can feel the love that went into making it...
But sometimes, I just add exes to my Sim's life for drama's sake... Usually, the ex is either the argumentative type, only there for the money or fame, or just generally not the best person to be around. The breakup is going to be nasty, but the Soulmate will probably end up meeting them once my Sim feels ready to get back into dating.
I also use exes to kind of deliver some karmic retribution to my Evil and Mean Sims. In their case, the partner usually ends up cheating on my Sim, they find out eventually, and give the soon-to-be-ex the boot. If they're wealthy, then don't think for a minute that the golddigger wife stays faithful: there's usually more then one Sim she invites over while my Sim is at work or otherwise not on the lot... Sometimes, if my played Sim has been particularly heinous, someone gets pregnant and my Sim ends up with an illegitemate heir that they may or may not know of. And it's definitely not out of the question for that illegitemate child to have the Good trait. Nope, those sims are not escaping karma just because they're a played household... :D
