William Middleton is the second son of Sir John and Lady Middleton. He has one older brother, John, and a younger sister named Annamaria as well as one other younger sibling whose name and gender are not known. He is around the same age as Harry Dashwood, making him four or five years old during the events of Sense and Sensibility, and Elinor Dashwood (the only unbiased judge) deems him the taller of the two boys when several characters debate the subject.[1]
His mother allows the numerous parties Sir John arranges as long as they are conducted in style and she is attended by William and John, whose troublesome behavior is sometimes the only reminder for the other guests that the insipid Lady Middleton is among them.[2]
His cousins the Miss Steeles spend their stay at Barton Park complimenting, doting on, and tolerating William and his siblings to win over Lady Middleton. When William violently pinches Anne Steele's fingers, his mother describes him as "playful." He tries to soothe his sister when Annamaria is throwing a fit over the scratch she received from their mother's headdress, but she kicks him away. William and John follow Lady Middleton and Annamaria out of the room in search of apricot marmalade to soothe her, though Lady Middleton tells her sons to stay behind.[3]