No. half-sister. It barely even counts.
My dad had an affair with another woman. Practically had another family in secret. Well, one kid anyway.
Parents broke up, he left, moved to a different country. Few years later he gets back in contact inviting me to his wedding 'cause he wanted to make it official with this skank.
I go meet his 'family' and his daughter, who's 5 years younger than me. Basically talked to her all night 'cause my family disowned him and I didn't know anyone else.
Stayed at his house, got drunk had sex. The end. I could barely keep it up because my head was spinning. Literally a few dozen thrusts. Didn't talk about it again and I never mentioned it to my dad. They live in England now so I barely see them