Not much change between Mainline Mark and Indomitable leading up to the start of Canon but the first point of Divergence is becoming friends with Eve in like Middle School rather than after getting his powers.
He ends up getting introduced to Teen Team early in their Team's career and spends a lot of his spare time at their Bridge Base, he acts as a mediator almost helping smooth over the other Members sharper edges while he also gets some extra-circular training.
He and Robot get close enough that Robot reveals himself to Mark and is pleasantly suprised to not be met by disgust.
Eventually when Mark's powers come in he works with Robot and Art in a Collaborative effort to make his suit, making it a homage, of sorts, to his Viltrumite Heritage & his Dad's first uniform (unaware of Viltrum's true nature), with a bit of his own flair and Robot's tech.
When Rudy comes up with his plans to have the Mauler twins grow him a clone body, Mark offers his own DNA for Robot to use, he also sees the potential in having his own clone so he asks for one too.
So Rudy ends up in a clone body of a young Mark and Mark ends up with a clone, but because he's not a psychopath like the Maulers, they don't care about who's the original, due to the timing, the Clones finish up around what would be the end of Season 1 so this time around Nolan's got two son's to deal with, still undecided on where to go from there.
So yeah, this is Indomitable my Invincible Variant.