Mono's name for what you want seems valid to me. And I agree, very difficult to obtain for the long haul, but if you are not necessarily interested in the long haul then perhaps you will find it for a time. Usually one person feels left out while the other two feel more connection and love for one another over time. The balance is near impossible to hold up.
Have a good look around here and you will find many who are trying to achieve what you seek...
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