Yes, since pictures cannot be exchanged that is surely proof that Lena knows her biological Dad, sure!I think is 99% impossible that Seymour is Lena's "real" dad. Lena's "real" dad is not an unknown figure for her, it's not like her mother doesn't know who he is or never talked about him.
So Lena has seen pictures of the guy and, probably, being told his name. She would have recognized Seymour for sure and most likely Charles (the bum) too.Python:l "Well, technically he's not my {i}real{/i} dad, but it never made any difference to me." $ fian = "n" i "I didn't know you had a stepfather." l "I've never used that term. As I said, to me he's always been just \"Dad\"." l "My real father left when I was two. I have no real memories of him aside from what I've seen in pictures and what my mother told me." l "But Dad has always been there since I can remember. He got together with my mom shortly after, helped her take care of me and my brother."
I would be less than surprised if Lena´s Mom did not exchange the pics of Seymour for some random guy, because she knows the moment Lena learns that Seymour is her Dad, the money Lena sends will go away forever.
Just remember that Seymour, no matter his pros and cons, treats Lena vastly better than her family ever did even on the worst playthroughs.