Edgar's birth certificate shows his D.O.B. as 10th July 1976, which is nine days before his onscreen father Benedict Cumberbatch's D.O.B. in real life.
Edgar's birth certificate shows his D.O.B. as 10th July 1976, the date of the CCTV from the morning he went missing is 30th April 1985, and Edgar is said to be nine years old. This would make him eight years old.