I dont see why not is evreyone involved understands that they will have to share and share alike and that any jealousy issues need to be openly communicated with all parties in advance.

My very first bdsm relationship was a polyamorius one with a male dominant and female submissive.

They were a married couple. I allways made sure that my participation in thier relationship did not overshadow thier pre-existing relationship. They and I agreed that alltough all things are not nessesarally equal due to the inherent hierarchy of a bdsm relationship (in our case He as dom, her as first girl and me as the new or low girl) that we must all have equal sharing priveleges with one another and equal say in the progression of the relationship.

In other words no sub/dom gets left behind physically or emeotionally and that is the hardest thing to accomplish in any poly arangment.

Good luck to the three of you!!