Hey khalil,

It depends on the airline agreements in place, but the vast majority of airlines do not allow for companions of any kind. The only exceptions I know of are Hawaiian Airlines, which recognize an enrolled friend (changeable every calendar year) and a few ZED carriers. AC, BD, LH, LO, LX, TP allow for companions, which could be anyone, HOWEVER the employee must accompany them. They're also charged at the ZH rate, which begins to get a little pricey (especially considering the routes that would go overseas)

Of course, these are true for my airline. Yours may be different.