Morrigan has sex with the son at the start of the game.
IMHO the problem here is considering Morrigan part of the harem or a love interest.
As far as we know she is a succubus(?) and she is the agent of corruption.
IMHO at the end the harem will be only the family (with or without Danny). If I'm right; so far Danny haven't touched any of the girls of the harem.
The banner itself seems support my Hypotheses.
Well with Danny wouldn't be a harem, that would be polygamy.
Standard form for actual harem would be any harem LI shown in game is only shown to do stuff with MC, before being proper LI. (doesn't mean they don't have a past, you just don't really show it in a harem route/game).
As for after being an LI... well that wouldn't be a harem in that case. would be polygamy, sharing, swinging etc. (context dependent)