Responses
I think you are right. He should have said something. It is an important part of his life, plus Ash wouldn't want for Karlyle to be blind sided like right now. But I don't think it's something he should warn his friends about. I think it's basic etiquette to not mention exs to the current partner in a party hosted by the partner as a way to meet them for the first time.
I don't know this blind sided ME. It evolved really fast, and in the side stories, I would have liked it more in the main story.
“Friends” that mention your ex when you are being hosted by the current wife and girlfriend should walk out the door. That is rude and they are just creating drama even as a joke.
Lyle now is clearly bothered, it is good Ash warned his friend but maybe he should have warn them before the visit. And of course Ash should have been honest with past relationships to Lyle so he didn’t have to feel this insecure even by accident.