The estranged couple -- who are currently separated -- came together Saturday in the ritzy Colorado ski town ... where Mauricio's been by himself over the past couple days, partying his face off and having a blast.

Of course, Kyle herself has been in Mexico of late ... but it looks like she might've just touched down last night. Now, she and MU and their kids are mobbing around as a unit -- with what looks like a private instructor/guide leading them up and down the mountains.

Like we said, Kyle and Mauricio appeared to be staying away from each other as they made their way around the resort -- and while each of them flashed smiles, respectively ... at one point they did, in fact, cross paths to face each other and that looked anything but pleasant.

Remember, they were doing the whole together-as-a-family thing earlier this year -- especially the summer -- and Kyle even showed up to support Mauricio during his time on 'DWTS' ... but as the months have gone on, it's now evident their relationship is strained.

While they've steered clear of the term "divorce" -- and, at times, even suggesting they're working on their marriage -- these last few days have been telling ... especially for Mauricio.

The guy's looked like a bachelor on a mission ... with the objective being, enjoy himself.

Kyle, meanwhile, has been preoccupied with her Morgan Wade doc ... and other ventures -- including what she's got going on at Bravo. All this drama will presumably be aired out on the new season of 'RHOBH' -- including, perhaps, an answer as to what's to come.