I'm about the same age as his wife. He was flirting with me more than a little for awhile. Then he got married to someone one I really care about, and have a lot of respect for.
This same guy flirts with me at family gatherings- I think he does it to screw with his wife, and honestly, as long as it doesn't genuinely bother her I can just go with it. If she ever tells me she wants it to stop it'll stop dead.
Then there are those times when I was in college where he'd try to talk me into sending him a pic. One he didn't want texted. Something to do with not wanting the wife to know. I texted him a really cute pic. Me in a crimson shirt as a redhead. He said that 'wasn't the kind of pic [he] meant'. Oh well.
He's a sweet guy. I know he doesn't mean any harm and would never want to hurt anyone he respects.