Sex life with my stepdaughter

Ever since I married Alice her 18 y.o. daughter has been giving me dirty looks and when she suddenly walked in on me taking a shower with nothing but a towel covering her young slender body our lives changed once and for all. That time she just gave me a blowjob right in a bathroom, but a few days later we were fully and shamelessly fucking even with no rubber. If my wife doesn't let me cum on her face, my stepdaughter will. Oh, lord!