You were not aware that your own husband was not related to this woman and other people call her sister, too? I think you’re making that up.

Surely you had met his family in the past to know if he had a sister or not (unless he does have one and was saying "I am going to meet my sister")?

Does she dress up as a nun?

I'm guessing this 'sister' is at every family gathering you attend, OMG just think how many times you've left them alone 😮

Maybe he’s into incest

I have a sister. I have never once called her "sister". I call her by her name, or her nickname. Never "sister".

Does she call him step-bro?

oh come on. you dont know who is sister is? do you and your husband ever talk to each other? this seems pretty out there.

Never heard someone call their actual sister, "sister"

Seems like you should have known who is or isn't in your husband's immediate family before he ever became your husband. Not to mention his propensity to hang out with hookers!