The scenes with Jack's wife/gf giving birth are way further into the future than the scenes at the cabin with Rebecca in bed (dying?). Madison is pregnant now, so the kids will be born within a year, and in the future scenes at the cabin the kids are what, 10ish? Jack is only a few years older than Kevin's kids would be. So these scenes take place around 10 or so years in the future.

So that means the scenes with Jack, Jack's kid being born, his sister showing up at the hospital, are further in the future. It also means that "they" are on their way (Toby says this about Jack) means some adult needs to be with him, cause he obv can't be driving himself. So maybe that indicates Kate is still alive at that point?

All of this is of course nullified if Kevin's kids at the cabin in the future scenes aren't the twins Madison is currently carrying, so who knows haha