Stan is Draco's twin, they were always there for each other but at first they didn't get along as all brothers do, but when their father Lucius Malfoy started hitting them, their relationship changed to a closer relationship, they took care of each other, they slept together since they were afraid of their father, come on, they never separated

They are now in their third year at Hogwarts and are still very close and almost always together.