Caught his step-father with his sister

He says that he was suspicious about his step-father and his sister but he never thought he would caught them having sex at home. That day his mother was working on the night shift (she's a nurse) and he had planned to have dinner and spend most of the night with his girlfriend but she got a call from her room mate saying her cat was not feeling well so after dinner she went to her place and he decided to go back home. When he got there this was what he saw and recorded with his cellphone. His step-father and his sister having sex in the bathroom.