The difference in the names Ann / Agnes are perhaps an error of transcribing.  The different reference numbers for the 1881 marriage are probably because one is the GRO and the other the Kensington Registrar's reference number. In the Death registers the name Agnes is probably the correct one (although she seems to have used Anne too) as that is also used in the Probate records.  Both Barrettos left a will naming a W.J. or H.J. Gates as the Executor, probably her son.  He died 23rd July 1900 and she 12th July 1902, both at Peckham.  There is a chance that these wills might mention any children of the 1848 marriage.  From the death registration Agnes was 69 so 50 at the time of her 1881 marriage so children from that 1881 marriage are unlikely.  She was already a widow with several Gates sons in 1871. Joseph Augustus had two sisters who in 1841 are living next door to a Potts family and are traceable forwards from there. There is much more that could be discovered, but I don't know how far you have already searched. Tomas Christie.