One is lucky to have a best friend in the world. Your life is empty and lonely without each other. Two best friends understand each other more than the lovers. They support and talk to each other and plan to have some fun together. Probably one would like to have this kind of relationship that is very crucial to be in the couples. And also, in this case, there is a limit to intimacy or not at all. Kissing might be like kissing your partner.
The passionate relationship is just opposite to the best friends relationship. You both partners are the true soulmates of each other. And it is your passion that you feel going to bed. We cannot guarantee the presence of emotions, but we can say that intimacy gives you pleasure. Even after that, you will feel alone and not loved. It is a temporary relationship.
This type of relationship is rare to happen. You both partners trust a lot with each other such that your partner can even choose someone else in your presence in their life. It seems weird, but the threesome will not have any problem with it.