then your story makes no sense for Tris/Charlotte/. Why the slow burn for the Mc and them if the moment they become aware of each other they become bi? it's silly for Tris/Charlotte but would work for the other girls as they have no other real characters than "lets all fuck someone and I don't care who" anyway. It's your game but if Charlotte/Tris become bi to solve the problem of the Mc the story becomes pointless. It's normal though so I never expect a dev to pass on the lesbo thing even when it is the biggest stretch to connect a mother/daughter who both develop feelings for the same person. It's easy, flashback to Charlotte being another pointless bimbo like Denis and Tris can just get curious and boom problem solved.If you don't want two girls to kiss/touch during a threesome, then just keep one path open. There will be combinations of girls that will simply work together. They will not fall inlove with each other, they will not have sex without the MC, but they will have good relationship, both with the MC and with each other.