People?

Why is it that the people you care about the most
always end up leaving or being rude to each other
I don't want to make it sound like I'm the best or the world revolves around me, because it doesn't. But I'm the root of our friendship and it's like they just can't get along...it's really annoying. I'm the kind of person that will make sure my friends are happy, but I will never let them be rude to me that just doesn't work, but when they start being messed up to each other then what are you suppose to do. Fist I avoided them then they said it got better now its like before...
My birthday is coming up, March 19th, and they both are coming and I want them to have fun! I want this birthday to actually be GOOD! All my past once have sucked! my 12th birthday was amazing it was me and 3 other friends and we went to an art fair we got drawn went out to eat and made cake it was amazing.....this year I want to take 4 new friends to the beach. Goal: see the sun set and rise, Bonfire with marshmallows, go in the water at night. We can't do that though if people can't stand each other or can't get along. If I have to leave some one behind then I will..I'll just go pick up Yali from Orlando she gets along with everyone!