I would not advise it. It can ruin a relationship if you are in one. It also comes with health risks unless everyone is honest and has a sexual health checkup.
Are you in a relationship? If so, it could end it. Do you want to see your partner with another person? Do they want to see you with someone. This images and memories will never go away.
Just my humble opinion.
It depends on what you have in mind. I have group sex and my husband enjoys it. But we did a while lot of talking beforehand and we slowly worked up to it. It hasn't really messed anyting up for us in the love and relationship area but it can for many people. Be very careful and feel free to message me about your specific situation.
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If she mentioned it then she'll do it just make sure you pay more attention to her the whole time even if you're getting off more on the other girl and then she'll let you do whatever you want.
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