I donít quite understand the question. A multi-wire branch circuit uses a single neutral conductor from the panel, run with the two (or three) phase conductors, to supply a number of loads. At some point at or near each load, the loadís neutral wire will have to connect to the branch circuitís one and only neutral wire. That is not a parallel connection, since there is only one wire going all the way back to the panel.
Can you clarify your description? At what point are these neutrals being tied together? Or are you talking about tying neutral conductors to equipment grounding conductors?
Charles E. Beck, P.E., Seattle
Comments based on 2014 NEC unless otherwise noted.