This one's interesting to me.

If Sans and Fell managed to get past the (most likely) passive-aggressive introduction, I think they would be great for each other. They're both very laid back and both seem to have a similar roll in their respected AUs.

The thought of them having a pun-off in front of their brothers makes me chuckle a little. X3

I imagine they would sympathise heavily with each other whenever something like a genocide route occurs. They may try to comfort each other to the best of their abilities.

There would most certainly be arguments. The different natures of their AUs ensure that. But I reckon they would make up pretty easily. They seem like responsible-enough adults, after all.

Overall, this seems like a considerably healthy couple. And, there's no denying, they're very cute together. X3

8/10.