[This page in draft. Still collecting and trying to verify.]
A few parishes of the Bucks 1841 census have been transcribed and are available free online. These include Aylesbury, Granborough, Hanslope, Hedgerley, Linslade, Tingewick, Waddesdon, and Wing.
John & Maria Brazil - This must be the John Brazele & Maria Garner who married 8 Jun 1829 in Worminghall, Bucks; Elizabeth Garner is presumably the mother-in-law, perhaps widowed? According to the marriage entry, John was from Albury, but the 1851 census records his birthplace as North Weston, OXF, identifying him as the John who was baptised 12 Jan 1806 in Thame as the son of John & Martha Brazil. Supporting evidence: The Susan Brazele who witnessed John's marriage to Maria will be John's sister, baptised 17 April 1808 in Thame.
Emma Brazell - Having three Emmas (two more below) born all within one year of each other must be unusual, and it's certainly confusing. So which is which? The Aylesbury Parish Registers record the baptisms of two Emmas in 1840/41. One is the daughter of "Thomas & Mary Brasil of Aylesbury, Barber" on 28 Aug 1840; the other is the "baseborn daughter of Mary Brazil of Aylesbury, private baptism" on 25 May 1841. This particular Emma is either the latter Emma, or one who was not recorded in the registers. To complicate matters, the James Drake recorded in the previous household married Mary Brazil 5 Sep 1841, so this Emma could conceivably be his and Mary's (but see the third Emma below). In the 1851 census, James, Mary and Emma Drake are living in Marylebone, Middlesex.
Mary, Charles & Emma Brazell - Charles (17 Jan 1835) and Emma (26 Aug 1840) were baptised children of Thomas and Mary Brasil/Brazil. Sarah Britnell (baptised 29 Oct 1830 as Sarah Britnal) is Mary's daughter from her first marriage to John Britnal, who died 22 Nov 1832, aged 22. Thomas, a barber, and Mary married 13 Jan 1834. But where is Thomas?
William, Thomas, Mary & Emma Brazell - I'm pretty sure that William and Thomas are siblings, children of Robert and Elizabeth Brazell, born 19 May 1805 and 29 Jun 1811 respectively. I suspect that Mary is the illegitimate daughter of their sister Mary, and that Emma is the younger Mary's "baseborn" daughter, who was baptised 25 May 1841. Could this Emma have been recorded twice for some reason (here, and with the Knibbs above)?