You can pick your friends, but you can't pick your family. I know that statement is true at times, but I wouldn't trade my cousins for anything in the world. I have grown up with them and they have become some of my closest friends.
They know all of your secrets, mostly because your parents have already told their parents. With that being said, they will have your back whenever you need it. If you are going through something, you know that you can always turn to your cousins for help.
They also know how crazy your family is, and they have to put up with them alongside you. You can always sit and talk about that crazy Aunt that shows up and always brings her dogs (we still love her and her dogs). Then you have your mom/dad and aunts/uncles talking about what they did when they were younger, all the cousins then turn and see how they can top it or tell your parents they are lucky you are a "good" child.
They have also lived all of your best moments by your side. From when you are your boy cousin danced around in tutus at your grandparents to when you casually sip wine (or juice for the young ones) at Christmas. The vacations you took with your grandparents and all of the priceless laughs that you have shared throughout your years of coexistence. Or the days spent out in the sun with all of your family just enjoying the summer and having some fun.
They were always there when something went wrong as well. Whether it be a death in the family, or a traumatic experience. They were there for your shoulder to cry on or if you just needed a hug. Cousins are the only people that have seen you at your best and worst, and still love you. We haven't decided if the love is because they have to or want to yet. (just kidding they want to love you)
You don't have to choose to be friends with your cousins, but I am glad that I was raised up with mine. There aren't any other people that I would have wanted to spend most of my life with. I love each and every one of my cousins. If they ever need me I will be here.