I cum in my stepsister's mouth after I caught her masturbating on Christmas day

My skinny stepsister is a sucker for masturbating and watching free Christmas porn videos, so I wasn't surprised when I walked into her bedroom and caught her riding a dildo. Watching my stepsister ride this dildo gave me a boner, so my stepsister had no choice, but to give me a blowjob until I cum in her mouth.