Stepsister, start studying, threesome

My stepsister has an exam tomorrow, so we study so she can get a good grade, but it seems that my stepsister is very horny, when we go to bed and she starts touching my pussy and masturbating, our stepbrother enters the room and sees how my stepsister He touches my pussy, he gets horny and takes out his cock to give her a deep blowjob. In the end we fuck hard making a threesome of stepbrothers and he makes an explosion of cum in my mouth