The show is a lot more straightforward than that. Garvey knew Jennifer was the daughter of Raymond Reddington. It was established in the show and is meant to be taken as a fact. When he sees the DNA report of the bones that says Reddington, he realizes Jennifer never had to hide from her father. Naomi most likely wanted her away from fake Red because Naomi knew he was an imposter. And Liz's DNA matched the one on the shirt from 30 years ago that is said to belong to Raymond Reddington. I think we're just supposed to take things at face value here. Liz and Jennifer are both real Red's daughters.

Thank you so much for this. Short and sweet and to the point.