As of right now, I do not think my future in-laws know that I was married before. I am 35 now and was married when I was 25-31. Met their son when I was 32. I mean it doesn't really matter, but it would be awkward if someone [aka my family] said something unintentially at the reception (where everone will meet for the 1st time). I mean if they ever asked directly I would tell them. I'm not tryng to lie about it, but at the same time the past is the past.
Just forgettaboutit?