first, we have she is not frank's biological daughter, she is the exact copy of her mother and she is having an affair with lilith. it is obvious that she will end up having sex with frank, maybe even with both, lilith and frank. second, there has already been a lot of debate about whether becca could be frank's biological daughter. also, there is a clue in BECCA RECKONING. becca, has calculated the timing of her mother's pregnancy, and has come to the conclusion that there is this possibility. she has in fact started a paternity test. let's wait for the second part, to find out the truth.