At what point do you break up a couple?

It depends on the story. For instance, Bella and Mortimer broke up in my save. Cassandra and Alexander now have issues with relationships so they tend to stray. Cassandra is on the verge of a divorce. Alexander and his wife have a fairly open relationship because his wife is just as crazy. Divorce does affect the children. I like adding consequences to kids due to the parents behavior. Some become very ambitious or some suffer the same fate and it becomes generational until someone breaks the curse..lol