Well, I would like him to be a son of Wm and Abigail Seaman, mainly because Abigail is on the census (in St Giles), so that makes it easier! lol They married in 1800 and had a son George bap at St Paul's Norwich in 1805. Unless Wm senr died one would expect more children .....it's just finding them! lol
Unfortunately there's no occ for Wm on George's bap or on the marriage for Wm and Abigail.
Was there one on the marriage cert?