Several parents of Team Kimba in the Whateley Universe. Chaka's parents are still happy together even with five kids, the oldest of which is about college age. Tennyo's parents have been together ever since they met while both working as mutant agents for the C.I.A. Phase's parents are in their fifties with about six kids and still together, even though Phase's father runs Goodkind International and is the richest man on the planet.
The Journal Entries contain a surprising number of these, considering most of the characters are immortal bisexuals who either don't have a real concept of monogamy or abandoned it long ago note (the stable, core character grouping is actually a trio, one of whom is a male exclusive homosexual, which doesn't stop him from having occasional sex with females, it just means he doesn't normally do so even if he has been sleeping in the same bed with one for the last 600 years). The implication in universe is that so many characters have stable long-term relationships because the culture does not expect anything specific beyond not being evil; not being able to handle it when your lover beds someone else is seen as a failing on your part.
Dan and Marc in you could make a life are a married couple in all but name long before they officially tie the knot. They do face their share of obstacles, but their love for each other always remains the greatest constant in their lives.