Yes it is possible, we are a fourple, and I love both of the women I have very much, it would be very hard to stop loving either one of them. My wife is my primary only in the sense we have to do day to day stuff together that my gf does not have to. She has her primary in that sense as well, although we do help each other out in many ways, we have even had some conversations around the four of us living together, although more in fun that or real but there has always been a ring of truth in these talks.
And in my book what is love, it means being friends, caring and doing things with the other, love has that feeling that looking at the other person and just having feelings, looking past the little things and loving the whole.
I ramble too much lol.