Unfortunately you show with this post that you have zero inkling what my discussion points are! If there is incest or not between Lena and Seymour is inconsequential for the main point.
Seymour is a very successful and connected businessman. It would be no problem for him to find/hire top- and supermodels for his photo hobby, BUT he chooses Lena, a rather unknown, relatively fresh model. He is very much simping over her, helping and favouring her on most paths. He is doing more for her than most of her family ever did.
Why would a shrewd businessman do that? There are only two options: Seymours sees in Lena the daughter he never had or she really is his daughter.
I once again mention the fallacy of your construct. Photos do not have to be the correct ones, esp. when showing them to a small child. Even if the photos are correct, people change and some persons change more than others. A beard or not, a different hairstyle is often enough to throw peoples perceptions off!