Someone's keeper

I feel like I am my friends keeper. When they need advice they come to me as if i am their older sister and i feel honored when I am able to help them. An example of this is with one of my friends she was having family and friend issues and told me about them and me and the help of her mom we were able to talk through them with her and resolve most of them so she was able to still have a strong relationship with them. Also i feel like i was the keeper of my friend Nadia because she had a friend who i thought would be a bad influence on her and she should not get involved with them. I pointed out the reasons why i felt the way i did and she listened to me. I feel like when i need one of them to be my keeper they are there for me, but most of the time i am the one that is their keeper and looking out for what is in the best interest for them. Lastly, I feel like I am my cousins keeper because he is only 4 so i feel like when i babysit him i watch out for him and keep him safe and out of trouble.