So tonight I just learned something &amp; it scared the shit out of me.  I had felt that something bad had happened to my twin sister even tho I haven't spoken to her since last February or so. 

It scared me &amp; I want to talk to my bf about it but I don't know if I should keep it in the family since it's not his business. Knowing my sis like I do, she wouldn't want me to tell him. But I feel like I should. But also shouldn't bc I don't even know how long we'll be together. If he was my husband or fiancé, it'd be different. 

Would I be the asshole if I told my boyfriend about the family situation? Please give me a clear answer bc he's almost out from work. 