Arthur FOSTER (1784-1858) married Ann PAYNE (1781-1860) on 08 Aug 1809 at Kirdford in Sussex. As far as I can see, the couple had five children, which really means that I have found five baptisms. The children were Mary (bap 24 May 1810 @ Kirdford), Martha (bap 09 May 1812 @ Kirdford), Jane (bap 02 Jul 1815 @ Wisborough Green), Robert (bap 11 May 1819 @ Petworth) and William (bap 02 Jun 1822 @ Wisborough Green).
The trouble is that with the exception of Martha, I can find very little about them after their baptisms. Martha is well documented, but the documentation for the others is very sketchy. There are records on the net, but it is difficult to positively assign them to one of the children. For instance, there is a marriage in October 1832 for Jane to Thomas Cooper in Wisborough Green, which looks promising, especially as her father is given as Arthur, but at the time of the marriage, she would only have been 17, which seems rather young. Moreover, one of the witnesses at that marriage is Martha FOSTER, which seems a good fit, the only problem being that by October 1832, Martha was already married to William BARNES, and would have been Martha BARNES rather than Martha FOSTER. Did she marry Thomas Cooper?
The other children are even more problematic. Robert (20) is probably in Wisborough in 1841 living with the HOLDEN family and working as a bricklayer. He may have died a few years later in 1845, as there is a burial in Wisborough in January 1846 of a Robert FOSTER (26). William (15) is with his parents in 1841, but then disappears. Mary I have no idea.