Although it is personal, at least one of its benefits presupposes someone else: the ability to guest someone (who has to fly the same flights as the SP cardholder) into the lounge. Allowing the travel companion (who, again, would have to fly the same flights as the SP cardholder) to go through fast track security would be a natural corollary of the previous benefit.
SkyPriority has nothing to do with lounge access.
SP is only for
- fast track security, where available
- priority boarding
- priority checking and baggage handling.
Where you may be confused, SkyPriority is often automatically handed out at the same time as lounge access - business class, elites... But for example, Flex Eco tickets have SP but don't have lounge access.
Also, there is no such thing as SkyPriority card or cardholder. SkyPriority benefits are flight dependent.