Since succubus-y demons
come in many forms
we can design our succubus however we wish. She can be dominant or submissive, parasitic or empowering, tangible or a dream creature, whatever. She can occupy Mom, or Sis, or both alternately or even simultaneously. She can be Lilith, queen of the succubi, or a low-level operative or novice, voracious or tentative, eager or bored, vapid or serious or a jokester. She can be totally schizo, leafing through multiple personalities. Can she die?
Let's say Dad brings home a novice succubus. He's her first. She's not really clued on how this succubus thang works -- maybe she's fresh out of succubus school (she was a C-average student). She tries many tricks, goofs a lot, but somehow manages to soul-suck the family whilst slapping flesh. Or maybe she learns humility. Does she turn away from the Dark Side?