The same thing's happened over me in 1st grade! Here's my advice, deal it out, and play with both of them at the same time. If they don't agree, claim that you won't play with either of them until they agree you and the two friends should play together. Friends shouldn't fight over other friends like tug-of-war, they should share them. That's how me and my two other best friends are still friends to this day. :)
