Janette,
This looks like your William:
William Child, b 16 Aug 1805, bapt 13 Oct 1805 Petersfield. Parents William and Ann Child, recorded as being of Weston. There are some siblings too:
James b 1 Aug 1808, bapt 27 Dec 1808,
John b 10 Oct 1811, bapt 5 Nov 1811,
Mary bapt 30 May 1811 by this time parents seem to be in Petersfield.
There may be others but the time frame seems too wide for certainty. William and Ann do not seem to have married in Petersfield.
Hope this helps you.
Nell