So, I had plenty of time to play The Sims 2 Ultimate Collection today since my internet was down so I played the Burb family first off. I got them a dog and cat and then got Jennifer pregnant. Lucy now has a baby brother named Thomas as a result. She's also a teenager now and for the first time I was able to age up an NPC kid she became friends with named Ratna. She actually is a decently pretty teen now as a result.
Then I played the Broke family. For some reason, Brandi was very attracted to Darren Dreamer...her turn-ons happened to be glasses and unemployed

but well...Family and Knowledge Sims go well together and since I never tried marrying them before during my original run of playing this game, I decided to go for it. So now Dustin and Dirk are stepbrothers along with Beau and Brandi's son Andrew (the baby that she is pregnant with when the game starts).
I think the main reason the attraction between them started is because they spent a lot of time together with when they greeted my new sim Tera McCall. (I created her so I could try out the Downtown/Nightlife scene. I never got to experience it originally). But oh well. Maybe I actually will have Cassandra and Don marry now. IDK.