Bedbugs - Yikes!

[Nancy Molinari]

I own a duplex and live on one side. The tenant came over last night to tell me they found bedbugs in his son's room and he was having someone come over today (Monday) to check out the situation. I felt like he was implying that they were there before he moved in 7 months ago, which I would find hard to believe that they would just now decide to start "feeding". I have the unit steam cleaned between ever tenant, but I realize that wouldn't kill any bedbugs from previous tenants. I've never had a problem before. I'm guessing one of his 3 kids brought them home from school or somewhere else. I don't want a legal issue. If they have tenant's insurance (as stated in the lease), shouldn't the insurance should cover it? Any suggestions or advice on this in case he tries to claim they were there before he moved in? I'm also concerned about those creatures coming over to my side, even though I have a fire wall.