DH is a leader with a youth group. There's a female adult leader there, 20 years younger than him. Until recently, she has had a shocker of a boyfriend who DH has quite literally wanted to punch, in (I presumed) a fatherly way IYSWIM.
When she first joined the group, I did wonder, as DH talked about her and her boyfriend situation quite a bit, but I have no other reason to think there's anything else.
I've met her a couple of times and she seems perfectly nice, was friendly to me, laughing with DH, but they both included me and nothing seemed untoward.
However, DH told me last night that one of the reasons boyfriend has given her for the split is that he thinks she's having an affair with DH. DH told me this in an "isn't this funny" kind of way. But, is it?