I'm sorry for you guys' loss. It's not normal to me, though. I know grief makes you do strange things....but....ehhhh....that's just plain icky. Was she super close with him before her mother's death? Like, a lot of hugging and affection? Were they a very touchy-feely family? I would keep an eye on their relationship in any case. They aren't actually related. Hopefully it was a one-time thing.

Also, the fact that she immediately called him after your fight and shared the details is highly inappropriate, worse even than the lap-sitting. That is a big red flag, which shows she does not have normal boundaries with him. 

I agree that it is inappropraite.

Though a father and daughter hugging and comforting each other over the loss of his wife and her mother does justify it.

That he is her StepDad adds an element that makes one go hmmmmm?

Though not unheard of, an adult SD being that close and  affectionate with her StepFather is rare and certainly is cause to give one pause regarding the appropriatness of ones wife sitting in the lap of her SF.

She knows it was wrong, she over reacted to your comment. She sounds to have deep seated issues regarding her parents.  Suggest Grief counseling for her.  

Yuck. Totally appropriate for them to sit and talk about mom,cry and hug a bit, but 30 minutes on his LAP? Not normal.

NFW is that normal. That is a creepy way to get comfort. If her mother was alive wouldve that been ok? Would she think I am so stoked my grown DD and my husband are so connected? Probably not.

I would totally keep an eye on that. How long has lap daddy been in her life?

Again very CREEPY

I guess I might be a little bit of a dissenter with my thoughts.

If this is a situation where her mother was married to her stepdaughter from a very young age for her?  Perhaps they really have a very "father/daughter" relationship.. especially if perhaps her own bio father is/was not on the scene while she grew up.

I guess I can see the potential for them to "cling to each other in grief at losing their mother/wife".. and that to attach another innuendo to what happened is really more in the mind of the person looking in.. than the nature and intent of what happened wihen they were comforting each other.

The fact that she said something about it.. at least in her mind.. there was nothing untoward about it at all... 

But.. I can understand how OP might have some level of discomfort at his wife sitting on another man's lap..

I'm not sure what happened would be different from a grown child crawling into their parent's hospital bed as they were dying etc... there is something humans crave in body to body comfort with loved ones (talking parent/child).. and maybe in this case.. that is all that this was.. ?

I agree with ESMOD. I think it depends on how their relationship was beforehand. If they have a strong father/daughter bond & he raised her from a little girl, I could see wanting to return to that time & crawl in Daddy's lap. Death of a parent is an extraordinary circumstance & especially if BioDad has passed or hasn't been around, the feeling of loss & grief can be overwhelming. My father died soon after I finished college. My mother had lung cancer and lived with me taking care of her for the last 5 years of her life. Yet I felt a profound sense of fear, orphaned and aloneness when she died.

Talk to your wife, suggest grief counseling. 

What matters is how you feel from this. Your DW was really insensitive the way she shut this down.  Instead of explaining to you that this is the type of relationship she has with step lap daddy, she swore at you. Defensive much? Time for you have some hot older woman to sit on your lap and "console" you because your wife hurt your fee fee's.

You have every right to inquire with DW about her interactions with SF. I can't imagine anyone being comfortable with that. They have very questionable boundaries with each other.

I can't imagine sitting in my own dad's lap as an adult woman. So, yeah, I think it's weird.

Comforting each other, sure, totally get that, but sitting in his lap? I mean, she was really sitting "in his lap"?

I can't give a good opinion because I don't know enough about the situation.

At first read, yeah, sounds totally inappropriate. But, ESMOD made some solid points. Human touch doesn't have to be sexual and is comforting. I could see how two people grieving saw it as an embrace that comforted them, and nothing else even remotely off came to mind. I'm also inclined to give the newly grieving a pass on werid behavior as grief does cause folks to do funny things.

However, I think the missing piece in all of this is the dynamic between your DW and her SF, OP. If he came around when she was past the "sitting in Dad's lap" stage of life, I'd find it concerning. Not that I'd jump to your DW cheating on you, but more her having been abused herself at a younger age and not totally understanding that the comfort she is providing may be innocent from her but not from him. 

I'm also assuming that your DW doesn't have the hots for her SF. If that's the case...you have a lot of other reason to be worried.

It's weird no matter what. Whether it's misguided-in-grief weird (which should just be looked past) or something-is-off weird (which needs to be confronted) is impossible to determine.