For safety and security reasons, visitors are not allowed on board. All major cruise lines have a "No Visitor" policy. This applies to all ports of embarkation and ports of call. Guests sailing will not be permitted to have visitors on board to see them off.
The only exception is when attending a wedding. Guests attending a wedding ceremony/reception or visitors attending any type of party/reception onboard that has been previously arranged by the cruise line wedding planner would obtain approval to board the ship.