I think couples most couples are randomized in the game. I think some have have a higher percentage of pairing up with each other in the end. Some like Jonny Zest, any of Partyhaus, Dennis Kim and Joaquin Le Chien have more random pairings than Lilith and Vlad or Cassandra and Wolfgang at least from my observation. I can't speak for other simmers out there. Even when I play vanilla because of updates until I feel confident enough to add mods back in Sims still pair up and have kids. I was surprized when taken away the marital ties of some that they would choose somebody else. I thought that Moira (Fyres) would still end up with Dominic Fyres because he seems more loyal devoted and loving towards Moira than Greggery Landgraab is with Nancy. I thought Mr Romero would still choose Miss Fyres who leads Paragon. I always forget her name but they are dating in the beginning of any new game except a few rare times. I can count on one hand the number of times they weren't dating in the beginning of a new game.
