Awful time for the families and friends of the crew right now.
I haven't seen anything on a third tanker being involved, but it's waaaaayyyy early yet.
I haven't been in the aerial refueling NATOPs for a while but I can't imagine they've changed all that much. The type of rendezvous used--if altitudes and offsets are not strictly followed--can lead to head-on setup. I've seen that myself--tanker blew by us off our right wing one night, co-altitude and not 1000 feet of lateral separation, never saw us and we were lit up like a Christmas tree. Ten miles isn't all that much room with a 200kt overtake or a 600kt closure.
And, as always, it's better to let the preliminary investigation take place. This happening during combat operations adds a whole other layer of complexities.