Tenzin and Pema married for love and are still in love after three, and later four, airbending children.
As of the Series Finale Varrick and Zhu Li get married after helping defeat Kuvira but only time will tell whether they remain Happily Married.
Homer and Marge Simpson; yeah, they have arguments and the like, but there is that sense that they genuinely love each other and they always bounce back. And when their current troubles do genuinely threaten their marriage, it's always treated as a Big F'n Deal, not just life as usual. It's quite possible that Homer Simpson is the most faithful husband on network television - certainly one of the most faithful. Especially odd considering beautiful single women keep throwing themselves at him, and he keeps turning them down flat. Not to mention at least one gay guy!
The Simpsons Movie. When the family is fleeing the town, the only valuable thing Marge takes is the tape of her wedding dance with Homer. Later, the fact that Marge recorded over part of the tape was enough to wake Homer up to how selfish he was and go off to save his family.
Hank and Peggy Hill with Hank probably the second most faithful guy on network television, experiencing several moments where beautiful women threw themselves at him and him turning them down.
Dale Gribble could probably be named the MOST faithful guy on network television. He worships the ground his wife walks on, pampers her, never says an unkind word to her, trusts her completely, the works. Even when his hero - a genius of an exterminator - throws herself at him, he pushes her away with a rant about his marriage vows that implies that he thinks his devotion to fidelity should be obvious to anyone, as well as mentioning that his wife "the greatest woman there ever was." All this is fairly undeserved: Nancy cheated on him for fourteen years and passed off her lover's son as Dale's. Considering that her lover, John Redcorn, is Native American and the boy is the spitting image of him, that's a testament to Dale's faith or stupidity. However, after she stopped cheating, they became at least as happy as Hank and Peggy, and much more affectionate. Of course, this is mainly because Dale never found out about his wife's affair - he trusts and loves her so much the thought of her cheating on him doesn't even cross his mind. Oh yeah... that's one guy who's never gonna mess around. Ever.
Oddly enough, this seems to be the case across the board with all the parents of the pre-teen protagonists of Codename: Kids Next Door. (Except Numbuh Two, whose dad is missing and presumably deceased.) In fact, while the heroes fight against evil adults and are suspicious of adults in general, their parents are an exception.
Numbuh One's parents were practically made for each other. He was the legendary operative Numbuh Zero when he was a kid, and as revealed in the Series Finale, his mom was actually Numbuh 999, the first female operative in the Seventh Age of the Kids Next Door.
American Dad! has Hayley and Jeff. The events of the 2010 Christmas episode indicate it may last.
Especially since Stan and Francine are ok with it.
By the end of season 6, this one has been averted and played straight in regards to status quo. Averted in that they're still married and have overcome a few marital issues, and played straight in that the show rarely brings up the fact that they are indeed married (on the infrequent occasions that Hayley and Jeff even appear at all). It's shown that Jeff has seemed to move in with the Smiths, and sleeps in Hayley's room, but most of the time he's nowhere to be seen.
The fact that Jack and Maddie are happily married in Danny Phantom is a justification Danny uses on Vlad Masters, who desires the latter. Even the Maddie program Vlad made admits that she's always loved the Jack program.
The Fairly Oddparents: Despite being utterly batty, Mr. and Mrs. Turner are a tight-knit, mutually supportive couple; most of the time, that is. Just don't let Mrs. Turner miss her anniversary dinner, or else.
David Xanatos and his wife Fox on Gargoyles. After their marriage we see them playing chess as foreplay, raising their son, Alex, and other such domestic bliss that one forgets they are both villains. Fox only married because she was in love with him and he demonstrated his love for her in a undeniable fashion; begging his worst enemy and giving up a priceless magic artifact in return for help saving her.
Mr. Carrot Cake and Mrs. Cup Cake, who run the Sugarcube Corner bakery and are rarely seen apart. When the Foal Free Press ran a gossip story about how 'the Cakes are splitting up' it was treated as earth-shaking news and the Cakes themselves were as shocked as anyone. ("We are?")
After going through hell to actually get married, Princess Cadance and Shining Armor. Cadance sings about 'loving and cherishing each day' and in every episode they're in after afterward, these lyrics are upheld.
The parents from The Replacements seem like an Odd Couple, but they love each other a lot. They are the only replacements who prefer their life after replacement compared to 'before'.
Moral Orel: Orel and Christina in the Distant Finale, when seen celebrating Christmas with their children. Still averted with Clay and Bloberta though, as evidenced by the photo on his wall.
In Scooby-Doo! Mystery Incorporated, Fred's real parents are Sickeningly Sweethearts. Daphne's parents are shown to be this as well, such as during their fake vacation. After the Cosmic Retcon, Ricky Owens and Cassidy Williams are this as shown during TV commercial in which they kiss. Sheriff Stone and Mayor Nettles, a happy couple before the retcon, have now been married for quite some time with four children.
In Samurai Jack, the Scotsman's relationship with his wife is... weird, but likely fits the Trope. He clearly loves her, and she goes from being angry at him (with him doing his hardest to apologize for every accusation she makes) to the two of them acting like Sickeningly Sweethearts. (In a later episode, he compares her singing to choirs of angels, although it's probably a matter of opinion; his own bagpipe playing is pretty bad. He also makes a joke about her weight to Jack in that episode, but then quickly add, "But don't tell her that, ya know how she is!")
Bob's Burgers - Bob and Linda have their quirks that bug each other, but are quite happy together, and get intimate quite a lot, sometimes inappropriately, like when they're chaperoning a school dance.
Mickey and Minnie Mouse end up married and are clearly happy together at the end of two Mickey MouseWorks shorts, "Around the World in 80 Days" and an adaptation of Shakespeare's A Midsummer Night's Dream, both of which later aired as parts of episodes of House of Mouse. The latter also ends with Donald and Daisy Duck getting married, and they also appear to enjoy being together in holy matrimony.
Marco's parents, Angie and Rafael, from Star vs. the Forces of Evil are both very cheerful people, if a bit odd, and are very affectionate towards each other, which can sometimes bother Marco. In "Diaz Family Vacation", we see they are both attractive towards each other when Angie plays with Rafael's chest hair and he gives her wife bedroom eyes. Also they were relaxing in the hot spring on Mewni, giving each other a romantic stare and made kissy faces that leaves Marco with a surprising reaction but Star Butterfly awing over them being "Sickeningly Sweethearts". However, in "Raid the Cave", Star seems in disgust over their affection after accidentally spying them leaning to kiss via the All Seeing Eye spell. Not only that, but Marco said in the "#Marco LIVE Animated Live Chat", in response to a fan, that his parents were "High-School Sweethearts" and loved each other for a long time.