It doesn't even invalidate the born in darkness part. I'm sure lots of prisoners were born in darkness. Talia is the only one that escaped. Like Bruce, she let down the rope and brought her protector with her. Also, it wasn't confirmed to be romantic love, which would be kind of creepy.
Oh yea, and addressing the part about being born in darkness. I just read more about Bane and apparently he was born in the prison.
But the disconnect is still there, because throughout the entire movie, the "born in darkness" thing was linked to the kid they kept showing. Once that kid is revealed to be Talia, Bane's background is a complete blank. Yea, apparently he was "also born in darkness" but you don't know for sure from the movie.
So my point still stands. Talia's reveal breaks Bane's character.