An update from the OP
We continued taking things slow. After about a month the three of us had a casual movie night that turned into more.
We still have some concerns but the organic nature of the experience has taken the lead, dissolving doubts when we are all face to face. There is trust, respect, passion, and love between us.
Thank you so much for the things to ponder. I doubt this would have happened without you responders! The three of us are agreed that this is the best threesome we have ever experienced cumulatively and the only word to describe the experience so far is surreal.
Barbie and I are getting tested together in a few weeks just for awareness and Ken was tested recently. I'm really happy!