A key photo lesson in these days of electronic family photos = keep 'outsiders' at the edges so they can be cropped out if needed.
I read all of OP's posts but still don't have a strong sense of what this picture actually looks like.
Whether OP is being reasonable or not turns on a range of factors, namely:
(1) Ex's prominence in the photo - are we talking about: (a) one of 10+ peoplel, or (b) a small handful?
(2) Size of photo: (a) a standard 4" by 6"; or (b) something much larger?
(3) Prominence of the photo - are we talking about: (a) a picture which is itself part of a 'bank' of similar photos, perhaps sited in a corridor or smaller room within the house, or (b) something that has pride of place above the family hearth?
(4) Whether the photo has aesthetic/sentimental etc value , e.g. (a) it's a cracking snap taken on a very special day, also is one of relatively few surviving photos that includes one or more beloved rels who are no longer with us; (b) it's just some random snap hastily taken shortly before the couple split up.
etc
etc
etc
Mostly (a)s - OP needs to get over herself, deal with it.
Mostly (b)s - OP probably has a point.