Its a human tendency or we can say this is a human nature that if they spend a lot of time with someone they start feeling for that particular person. By their own a unique feeling for that person generates automatically. Sometimes they loves them so much that they count that person as their family members. Like if a guy has best friend his cares him a lot and calls him brother and really he loves that guy whome he calls best friend he loves him so much that he used to share everything with him if its the matter of love or its the matter of party or its the Matter of going on shopping or chilling what ever it is he wants that guy to involve on his happiness as well as on his sadness. Same on girls side if they met a girl and start their conversation then they even don't know how this girls took her heart and became so special to her she starts calling that girl her best friend and use to give her many cute names. She always wants that girl to be the part of her happiness as well as sadness too. She always calls her to chill out and for shopping or for any tour. That feeling attach the humans to humans and creats the unbreakable bond but what happen if they live them suddenly? Its not sure the girl or boy whome they calls their best friend they don't have any other friends. They tells all their secret to him or her as knowing him or her a friend may be this could be happen they are also having other best friend and they tells all their secret to them then  slowly slowly all people came to know all the little little things about that particular person suddenly and after that his heart just got break and he or she never wants to make a friend like this. 

So if we ever wants to make a best friend we should make our parents our best friend. They are the only person who will never cheat us never ever. If we can't open a lot or can't be frank with our father so we can share or all things to our mother. She is the only person who will understand us anyhow and never ever tries to break our trust. So love your mother never let her moral down.