A family of taekwondo instructors stopped an attempted sexual assault and pinning the attacker until authorities could arrive, officials said. The An family, which operates the Yong-in Taekwondo dojo in Katy, a suburb of Houston, heard screams coming from a neighboring business at around 4 p.m. Tuesday. They thought it was employees playing around, but then a “final scream” sent the family running into the store. They found a man on top of a young woman who was trying to fight him off. An’s father Hong, a taekwondo grand master, rushed to pull the attacker off the victim. His children, all fou…