TIFU by inferring my husband was my step-bro

My husband's father, who is in his 80's, got sick and we went to visit him in the hospital. At the front desk, a guy was checking us in and asked us our names and our relation to the patient.

My husband easily said, "He's my father".

For the life of me, I could not remember the phrase "father-in-law, " so I just stood there and blurted out, "He's my stepfather."

My husband looked at me and started laughing, and the clerk even chuckled. I was so embarrassed, I said, "No wait, that's not what I meant, this is my husband and that's his father."

But it was too late, the damage was done, and now I'm being called step-sis by my teasing husband. Oh well.

TL;DR: I slipped on my words and accidentally suggested my husband was my step-bro because I couldn't remember the words father-in-law.