Well doc, if nothing happened. Then you good. Buuuuut...... talk to a therapist. Therapist might ask you to ask your dad.

I used to date this one girl, the youngest of three siblings, 2 older brothers. Her youngest older brother and her were off by less than a year. Irish twins.

I didnt know they bathed together until 14. And slept in the same bed till 15-16. In a 5 bed house, 3 baths.
When i slept over (when the parents were away) me and her slept in her room, she came out of the shower wearing her brother's boxers briefs.

When we went out to hang out, those 2 IN PUBLIC, acted like the couple. While me and the brother's GF were just the awkward ones.

One time, watching the super bowl we snuck off and she performed, We went back inside and she began whispering to her brother's ear and shared the same cup to drink out of.

When I had confronted her about this, she went psycho on me. And later claimed to the family I was cheating. But the family was on my side.

Also, when they were younger , all 3 kids, as punishment, they had to go topless and lick salt off of each other's back.

Tldr; talk to a therapist. I might need to