I have a club membership. A friend is traveling with me, but not on my itinerary. Can my friend come in with me?

I recently brought in a guest who was flying Southwest (i was flying UA). I am not aware of any requirement that your guest must also be flying United).

I don't think so. Unless they are 1st class or business.

If they are flying united Also yes you can.

All you can do is try

Officially no. Depends on the person up front

If they are flying United, yes you can bring them into the lounge

I don't think so. Give it a try, but since they aren't on your itinerary it probably won't work.