What's the best way to explain how they're related?

The Summers family is weird as we know, and this is one of those things that make my head spin a little when I think about it too much, so I figured I'd get other opinions.

I know each character, though I wouldn't say my on an encyclopedic level, but well enough. I just wonder what would be the definitive way to look at them.

Nathan Summers, aka Cable, and Nathaniel "Nate" Grey, aka X-Man, are considered to be both alternate universe counterparts, and half-brothers of each other, though I wonder how applicable "half"-brother is considering that Cable's mom is a clone of Nate's mom. Also, there's the matter of Nate himself being the result of artificially breeding Scott and Jean's DNA by Mister Sinister and thus never actually knew them (he was raised by Forge instead).

Basically, Nate is Cable if he never had to contend with the techno virus eating away at him from the inside, thus he never had to keep it at bay and was free to use his powers. Powers, that I should say are godlike, however he found out that said powers can kill him, forcing him to greatly reign it in lest he die causing Nate to often fight below his weight (and fail whenever convenient) and he's been nerfed by a lot in the past just so he doesn't end stories by existing.

Nate is also considerably younger than Cable, roughly early 20s (by my best guess) while Cable is somewhere in his fifties or beyond. Cable, when unrestrained, is probably even more powerful than Nate, if only by way of his experience and intellect giving him an advantage, because Cable is already a very dangerous individual without his powers having grown up for decades in a futuristic war.

But anyways, how would you say Cable and Nate are related? It's confusing to say that Nate is Cable's "alternate universe counterpart" and "half-brother", because the former suggests they're two versions of the same person, while the latter suggests they're two different people that are related. Also, as said, Madelyne Pryor being Jean Grey's clone... does that muddy up that "half" aspect at all?

Just wondering what you guys think.