He is not with Thomas & Fanny in 1841, they do have James age 5 and Robert age 4 there. H0107/568 bk18 f54 p18ADDED I wonder if James was mistranscribed by enumerator and should be Thomas
This looks like 1841 for Jane & familyPiece 557, Book 12, Folio 13, Page number 19Liverpool. All born in countyJames Young 30 marinerWilliam Young 5Margaret Young 30Jane Young 42 (this looks like age 2)Margaret Young 9 MoCas