Weddingbee boards

We're trying to nail down the wording for the invites - we're going the more formal route, with my parents hosting, but my FI's father passed away ten years ago and his mother has remarried.  Question is: what do I put for the "son of" part?

Son of Mrs. Kathy Smith Jones (his name is Smith, she goes by all three)

Son of Mrs. Kathy Smith Jones and the late Mr. Michael Smith

Son of Mrs. Kathy Smith Jones and Mr. John Jones (he is close with his stepfather, but not as a father)

I don't want to offend his mother/stepfather, but he's not really the son of his stepfather... I've tried asking him, but he hasn't really figured out that this matters yet. I could call his mother, but don't really want to if I don't have to :)

Help!

How long has his step-father been around? Out of resepct for not only his moms husband who has been a supporter and to his late father I say include all three.

Son of the late Mr. Smith and Mr and Mrs. John Jones.

That's just my opinion. But i never like leaving someone left out that is important to my parents. My dad remarried and I included all three parties.

Oh, I hadn't though of that, that's another great option. His mother remarried three years ago, so not the longest relationship with him, but we live near them and no one else in our family, so have spent many holidays/weekends/etc with them both.