Here's what I remember: Liz is pregnant with Future Max' baby. She and Max are not on speaking terms. She might or might not have left Roswell for a little while. If she left she must have come back before the baby was born because she gave birth (after a difficult labor) in Michael's apartment with Max' help. I think he had to use his healing powers. The whole thing is really painful for Max because of Liz' infidelity, so he wants nothing to do with the baby although I remember a really awkward scene in Liz's room where Max comes to check on her to make sure she's ok and at some point she has to breastfeed the baby (whose name is Alex - I think). Max' parents get on his case about being irresponsible because as far as everyone in town knows (except for the pod-squaders, of course) the baby is Max', so he ends up looking like a dead-beat dad.
At some point Max and Liz slowly but surely begin to reconcile. Max starts bonding with the baby who - technically speaking - is his son. In fact the breastfeeding thing might have played a part in that. The clearest thing I remember is a (4th of July?) picnic which includes the friends (maybe even the parents) and Max, Liz and the baby bonding. We're left with a kind of open end to the story. It's four years later Max and Liz are definitely together (so are the others) but their future is precarious at best.
Sorry for the lengthy post but I tried to put in as many details as I could recall.
If someone can help me find this fic I'd be ever so grateful. Thanks!