You know they're individuals and there isn't any guarantee they'll get along with anybody. I have two Quakers and though Jade wants to be friends, Clyde doesn't, and they have a sort of armed truce. They do enjoy talking to each other (or maybe it's a competition to see who knows the most words and sounds

) but they don't play together. Last night, for example, Jade flew over to Clyde's cage and sat on his open front door and he came out and hissed at her and she hissed back, and I had to go intervene. I don't think they would have actually fought, but better safe than sorry. Clyde is King and that's that, and he doesn't want to share attention, time, or anything else.
The usual advice is don't get another bird unless YOU want one and never get a bird for your bird, and it's good advice. They might like each other, they might not, and even if they do, you'd still want to have separate cages so they don't decide to form a little birdy cult and exclude you altogether. Now, you can generally put two budgies together and after a little shuffling to determine who's boss, they'll get along fine. My two certainly do. You can often put two dogs together and they'll eventually be friends. My two dogs are practically Siamese twins. But that just doesn't hold true for Quakers.