Who is Ned Freeman from About a Boy and what is their importance?

Ned Freeman is the two-year-old child Will makes up in order to join SPAT. Will tells Suzie that he and Ned's mother, Paula, were once married and that he got full custody during the divorce. Ned is a means to an end, but he becomes something of a real person in Will's mind for a short time as he goes to extreme measures to convince Suzie of his parenthood, including buying a car seat.