I was going to mention one in between. BTW they do not have to be GFCI's. They do require GFCI protection, if there is more than one they do not have to be on separate circuits. They can have other outlets in same room on with them, or they can be on same circuit that is feeding other bathroom receptacles.You can install one gfci in between the two sinks and be compliant. The receptacles need to be within 36" of the edge of the sink.