A large chunk of Karkat's ships are a direct result of his "I CAN FIX THEM" complex, so I'm going to dial that up to eleven and have him date Eridan, Vriska, and Gamzee at the same time. No one knows what quadrant they're in, least of all him. Karkat just knows he's going to put these people back together if it's the last thing he does.
It's really dysfunctional. The only one with any working idea if how to show proper affection is Gamzee, which usually results in him dragging his partners kicking and screaming into the horn pile. Eridan just throws extravagant presents at people and Vriska follows his lead while pretending he stole her idea because she clearly doesn't need any help with her emotions. Horn pile cuddles are filled with multiple variations of "I'm not enjoying this, I just happened to agree to it, shut up" whilst going on for hours because 3 of the 4 involved are monumentally clingy.
Somehow, it works and everyone somehow becomes a better person. Vriska genuinely apologizes to Tavros and tries to make up for what she did, which just gives the poor boy an existential crisis. Gamzee has a support network to fall back on when his sopor runs out and Eridan is able to hold onto his hope because of all the people counting on him. All four members have the sudden realization of "oh my god, these people love me and won't abandon me ever" at different points and spend the rest of the day hugging their nearest partner. Somehow, they actually managed to make things work.
At one point, Karkat realizes he didn't just fix them, they fixed him too.
Also, Gamzee would bring his two boyfriends and girlfriend along to raise the cherubs. All hell breaks loose as these four try to figure out how to be parents.
