I'm not a big fan of telling people to "deal with it." If I can offer ways to get to a place where they feel better or are on a path that works better I will because it shows a level of care that I like to show.
If I were in your situation I would give little details, stick to my boundaries as best I can and stay empathetic to his. I would also do a tag search here for "jealousy" and read up on how he might deal with it. Maybe read it with him.
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