Girlfriend’s stepsister gave me blowjob while Gf was not in the home

I came to my girlfriend’s house. I saw that she was not in the home. I ask her stepsister about her, then she said that dad took her with him to a party. I started going to my home but she stops me and opens my pant. Her mom was in the home but she did not saw us. I was happy that my gf’s stepsister gave me blowjob.