How did you guys hold it with your spouses family? Did you go dark on them when your spouse went 'dark' on you and let WAS handle everything by herself? If she tells them, and I think she will soon, they (at least some of them) are going to approach me. I'm planning on defending the situation and not make my W look bad. I want to stick with my DB plan. The family involvement definitely has potential to blow up, some of them will go viral.
If your wife handles discussing the situation with her family by herself, she will undoubtedly lie to them. Well, actually, she will more likely sugarcoat it and lie by ommission.. She won't discuss OM and his involvement at all, rather, she merely tell them X, Y and Z about your relationship as the reason(s) you two are splitting up.
She has every intention of introducing her new soulmate OM to her family AFTER she has established that your marriage is over (and thus she is free to start dating).
If they approach you, your best bet is to tell the truth.
The internet is 90% complaining and entitlement and I hate it because I deserve better!