In my recent save, I built a basement in the Goth household and furnished it like a bedroom/gym and it had it's own bathroom and all. I had Don move in as like the person "renting" it out because he was getting overwhelmed by the Caliente girls. I had him start an affair with Bella Goth and got her pregnant. She left Mortimer and her kids hated her for awhile (I didn't mend the friendship until they visited or asked to hang out without me controlling them). But Don proposed to her and they moved into one of the one bedroom homes. They now have 3 kids, Rose, Omar and Kira. They did eventually get married. But he had a brief affair with Dina but she got way too clingy calling to hang out every night so he called it off. He briefly romanced the guy next door.
Cassandra and Alexander do talk to Bella again, not as close but Cassandra is married to Malcolm Landgraab with a baby on the way.
Don is a great dad but he definitely still has a wandering eye, he's always flirting with people. Bella is no better, she's currently trying to mend her relationship with Mortimer (they were enemies) for their kids sakes but they keep having a cheeky flirt now and again.