The relationship between Pinpin, Rubilax & Evangelyne is one I find... fascinating.
I don't have to explain to you the Pinpin/Evangelyne side of this equation- canon does it well enough on its own. Same with the Pinpin/Rubilax side of it. They're basically soulmates in fighting.
You might want to hear about Rubilax and Evangelyne's dynamics though, because they are... fascinating to see. The first time we see them interacting directly is during the whole "save Tristepin" arc- while Rubilax is busy on his power trip, Evangelyne banters with him. Granted, fun banter is common in Wakfu, but it's still noteworthy that Evangelyne absolutely refuses to entertain Remington (cutting to the chase with "ok what do you want let's do this fucking deal" while he's flirting with her) while she lightly makes fun of Rubilax while using his body as a stepping stone. There's also the fact that she pegs him as a "good guy playing at being a bad guy," which is really self-explanatory in how she perceives Rubilax- she doesn't think of him as a threat, and clearly hasn't in a very long time.
Another moment that struck me is during the Bellaphone episode, where Evangelyne immediately trusts Rubilax to possess Pinpin to get them all out of here. And he lets her climb on his back too!! They're battle buddies in the same way Tristepin and Rubilax are battle buddies, which means a LOT for a shushu.
When it comes to ot3s, it's usually easier to analyse every couple dynamic and see how it plays out, but in this specific case I think seeing how Rubilax acts in the context of Evangelyne/Pinpin being a thing is also super interesting (as opposed to how he acts when he's alone with Tristepin or Evangelyne.) Pre-family life, Rubilax is quick to meddle in Tristepin and Evangelyne's relationships, taking Tristepin's side when they have a lover's spat (significant because prior to his character development he would have found a way to hurt both at once.) Post-family life, he's clearly some sort of parental figure to the kids, since he lets Elely use him with 0 hesitation (and Elely even has a lil plushie of him!) He's not just "dating Pinpin" or "dating Evangelyne" or "third-wheeling them both"; he's involved in their relationship as a whole.
Also you know, Rubilax canonically watches Pinpin and Evangelyne have sex. Like. That's a thing. That's canon. You ever think about how that's canon? I think about it all the time.