I didn't dismiss anyone's trauma, I'm asking if that has ever resulted in anyone's trauma, a parent showing their adult child's partner a picture of them naked as a baby.
I mean if nothing else, not as a "torture," showing the partner the first couple of pictures of the kid as a baby should be acceptable to people just as a "this is what they looked like when it all began" and they don't come out with clothes on. They also are unable to understand the concept of consent, let alone give it.
I would also suggest that if that did cause someone trauma, it would be because the parent was aware this sort of thing would upset their child to that level and did it anyway. I think most parents wouldn't actually show the pictures if they knew it would cause the child real psychological pain, because that isn't the point in doing it. It's usually a form of good-natured ribbing, not malicious.