Well, first I would confront your son (19 or not) about his lack of respect for your privacy. First for 'snooping' and second for opening his mouth to anyone. Why on earth would he talk to one of your neighbors about something like that? Have you talked to the neighbor? If they are divorcing over an infidelity (possibly her's), he may think she was 'influenced' to look else where.
Not enough details here to make a sound judgement other than talking to your child about privacy, respect, and spreading gossip/rumors and the pain in can inflict (even if it is unintentional).
Good luck,
Maria
