Is it wrong that I want to tell my sisters husband about her past?
That seems intrusive. Why would you want to tell him about your sister's past?
Because I think he deserves to know the truth about her.
You shouldn't just tell your sisters secrets from the past like that. You should leave the past behind and not be cruel to your own family members or else they may shut you out of their lives.
I just think he has the right to know, and if she's not going to tell him then someone should!
It's not appropriate to talk to your sister's husband about anything from her past. Doing this will make you troublesome and intrusive.