Two people who've met when they were young (in the womb) and come together as buddies years later. They are special, and everyone knows they are the Bestoes.
Person 1: OMG! There's the Bestoes, they texted in the womb!
Person 2: They're so cool!
When you are forced to leave a group against your own wishes and the group achieves success or happiness without you.
Pete best was fired form The Beatles, and replaced by Ringo Star; before the Beatles reached commercial success.
I got Pete Bested when I was cut from the team and they went on to win the championship.