I disagree with his assessment that you can't have a partner who is a "best friend". I think that's essential to true intimacy with someone. That said, a sister? I know someone who said she felt as if she were walking down the isle with her brother. Ouch! The marriage ended in divorce. It appears to me he does care a great deal for you, and your friendship is highly appreciated by him. That seems to be reflected in telling you all about his 4-way, and everything else that could hurt your feelings -- knowing how you feel about him! And that's a big problem. No matter his motivation, if he were sensitive to your feelings, rather than having a selfish approach to this friendship, the pain you're experience might be minimized. There's no magic potion you can use on him to get him back. The fact remains, it's more hurtful to be that "best friend" than it is to wean yourself away from him and, eventually, seek out other relationships. I don't see a great deal of hope that you and he can be a couple ,again, but it's best to show independence -- to free the hold he has on you. And he must be aware of it. Your life should not revolve around him. You, no doubt, have a great deal to offer in a relationship, but you do not want to be with a guy who told you this: "I was more of his "best friend/sister. AND that in a relationship, it shouldn't feel your partner is your best friend." Again, I disagree with the "best friend/partner"assessment he has made,  but the sister correlation speaks volumes.