This is not unrealistic at all. Your partner should be a little more concerned about allowing for a cooling off period out of respect for you. That being said, you should speak to him, express your concerns and he can in turn explain things to your ex so it does not overtly affect their relationship. Don't count on him reading your mind. Sometimes people do things without even realizing who they are affecting. It's not malice, just absent mindedness sometimes.
Playing the Game of Life with Monopoly rules.
Monogamy might just be in my genes
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