Home Harem how to get it without the bad ending:
side tip: It would work faster if you use cheats.
First, you need romance Sasha or Bree first. Honestly, it's super easy to romance Sasha first because her events are not super hard to get to. While Bree it's easy just to do the maid path honestly.
The Goal is:
Sasha need 75 Love Points, 75 Kink Points and 50% Lesbian points (Just use the cheat to bring it to 50% but be careful because when you have sex with her it'll get lower. So also reset it back to 0 and bring it back to 50%). Also, have sex with 3 times.
Same thing with Bree but the maid path is just quicker for me in my opinion.
Just make sure both of them have the same requirements, then you have make sure they both girls are in the same room so they could confront Mike and then they'll ask if he's dating anyone else? If you're going to do the Sam or Step Sister or both path then say yes to seeing other girls it won't ruin anything. Then if you completed all the requirements I gave for the Home Harem then they won't break up with you therefore, the harem will be unlocked.
Now, adding Sam to the Mix:
Just caught Ryan at the club then show Sam the photo that he was cheating and then she'll come over drunk and yes you love her then you'll have sex with her. Afterwards bring up her LPs first then talk her another day, then Sam and the MC will go out on a date then on another day bring up her LPs talk to her then she'll confess her feelings accept them. Her points should be around LPs should be around 80 and her Kink points should be 65+. She will ask you are you seeing other women, say yes make sure your kink points are high for her to not be mad. She even suggest she might want to join the fun.
How to get Sam into the Home Harem:
Talk to Bree and Sasha then call Sam then boom she's in the harem.
To be honest: I don't really care about the Step-Sister being the harem. I might do it or not it depends.