Killer break-up line #3: "You've become like a sister/brother to me"

On one point, this break-up line has a certain brilliance to it. For starters, why would you want to be with someone whose feelings for you have changed from romantic to familial? What's more, it's got the "ewww!" factor. The last thing you both need is this kinda, sorta incestuous thing of sorts, even if it's just a feeling. Of course, what choice is there but to break up?

It's a killer line because: how can you argue with this when there's no more passion for you?