A scene in Sisterly Lust shows it perfectly. MC take a walk and happens to see his mother and eldest sister together and after a bit of conversation they make love. We know they love the MC, by this point they are carrying his child and have all moved to the island together but it also shows they love each other just as much.
It's the only way for a harem to works anyway. Well, unless you do it the old way ; I'm the prince, here's your now living quarter, be aware that the guards will not let you go out. For a nowadays harem to works, the girls need to also love each others, and this as much as they love the MC.
The love for the MC is needed since they'll share him ; they let him do what he want with who he want, because they love him and know that it's what will make him happy. As for the love for each other, it's needed to avoid jealousy ; they'll be happy even if they haven't had an alone time with the MC for a whole week, because they love the girls who had this chance and know that it made them happy.
And once again it's shown in the games you named.
Haley's Story being probably the best example for this. Haley don't care that her brother is with Sandra, because she like her, and it's reciprocal. But she also ask him to stop fooling around with other girls ; not that she personally dislike them, but she don't know what Sandra think and feel that it could hurt her.
It's the only way to have a believable harem in nowadays setting. Well, unless the girls are totally brainwashed.
Point is it is the MC's harem, he is the man of the house but he's comfortable in the knowledge they also love each other. There is no jealousy because they are all free to explore their feelings for other members of the household.
Anyway, wouldn't it be totally hypocritical to do otherwise ? Mom, you'll have to share me, but I'll not share you, not even with your daughters... There's something wrong here, and MC's feeling can be questioned ; is he really in love with them, or is he doing this out of pure lust ? If really he loved them, why deprive them of a possibility to be even more happy ?
This being assumed that another man couldn't make them more happy, to appease the NTR haters out there.
There is just something special about a family willing to explore the taboo together as equals, no corruption, no coercion, no magic and no mind control just pure love.
Totally. It's what incest stories initially were anyway ; a love so pure and deep that it don't care about the rest of the world.
It's one of the main reasons I can't get into most incest or even harem games. There are too many people playing them that need the MC to be the only one getting any action which leaves people sat around doing nothing and it's boring as fuck.
It's boring because, as I implied above, the MC don't act out of love, but out of pure lust. Yet, there's surely some ways to have an interesting story with a MC acting just out of pure lust. But for this, the said lust need to have a reason, and a meaning in the story ; and by "reason"I mean something else than some succubus choosing the MC.
I Don't know, it can be some mental illness that make him have an insatiable lust, and the girls who love him accept to join the harem because they want to be with him (which is different to "have sex with him"). But then, the story have to talk about this illness, to show the MC struggling with it. He want to be faithful to his girlfriend, then the said girlfriend open him to other girls, because she clearly see (and it's clearly shown by the game) that he suffer from this faithfulness ; not because he want to have sex with other girls, but because he need it.
Such pitch would have made
WVM effectively interesting ; it would have been way better than the initial girlfriend just being a creepy cuckqueen.
It's also incredibly boring when that incest happens through blackmail, magic etc.. It seems like a cheap and easy way out and there are no feelings behind it.
It seems like this because it is this.
In the exact same way than incest is the easiest setting for a sex game, blackmail and magic are the easiest way to make the girls have sex with the MC. There's no need to give them a personality, they would be going against it anyway. And there's no need to show how the MC achieve to seduce them, nor why they fall in love, since he don't seduce them and they don't love him.
You don't know how to write and want to make a harem game ? Use a MC that will blackmail or brainwash his family, you can't fail... but you can't win either.