*EDIT* -- I'm so confused/curious/concerned

There's this guy I used to be friends with in high school. Although we haven't talked since then (we are early 20s now), we are still friends on Facebook. He and his wife have had 2 kids, but out of no where, they stopped posting and talking about their first son. All of the old photos that included him have been removed. It's as though he never existed. All their posts only talk about their second son now. I have no idea what happened to their first. I don't want to ask because it's not my place. We have not talked in years and I don't want to bring it up in case something bad happened. I don't know what to think. I think it has been about a year since I last saw them post about their first son.

Edit- I just searched for an obituary and did not find anything. I also tried just searching his name to see if maybe there was a news story about anything, but nothing. I can not think of any other explanation. This has kind of been bothering me for about a year, ever since they stopped posting about him. They seem like good parents, so I can't see them having him taken away, even if that were the case, I'm sure their second son would have been taken away as well.

Can anyone think of any other explanations? I really want to message him and ask, but I know that wouldn't be the right thing to do and I could never bring myself to do so.