Whilst tracing the Batchelors through the Census records, William (1817, Bosham) appears in 1881 with sisters Ann Batchelor and a married Jane Trevett (c1818, Bosham). After checking the Bosham and Westbourne Parish records, I can find no Baptism or Marriage record for Jane Batchelor.
In earlier Census records, 1851-1871, Jane Trevett appears with husband Edward Trevett (c1801, Bosham) and their children. Unfortunately, I've been unable to locate a record of them, married or not, in 1841. The oldest child in 1851 is born c1840, possibly indicating a marriage before 1837.
In 1871, Ann Batchelor is shown in the same house as Jane Trevett. Shown again as a sister in law to the head, Edward Trevett, Jane's husband.
It's difficult to prove that Jane is the sibling of Ann and William, but the circumstantial evidence is compelling.