The only Richard Kew of the right age that I can see on the censuses in the 1841 census; a bookbinder living in St Pancras, married to Mary. 3 children - Mary, James and Maria. Is this the right man?
It says that he was NOT born in county (Middlesex). I note that there was a gap between his birth and baptism - could his parents have moved into the area in that time?
I also see that he named his 2nd daughter Maria. Looking at Kew children baptised to a James and Mary, there was a family in Fiskerton, Lincs, having children in this time, but I don't think it will be them as the Lincolnshire baptisms span either side of Richard's baptism. But there was also a Maria Kew, d/o James and Mary, baptised at the age of 21 months in Westminster on 1 Jan 1806. Any connection?