The other way to come at it is to use marriage certs and parish registers
The marriage is on FreeBMD
( http:/freebmd.rootsweb.com/cgi/search.pl ) as being in the Dec quarter 1849 in Newport Pagnell registration district. If you order the certificate you'll get confirmation that his father was William.
Similarly you can order and view the microfilm of Cranfield parish register at your nearest LDS Family History Centre to confirm Josiah's baptism
This looks like the family in 1841, but no sign of William
HO107/56/17 folio 11A
North Crawley, Bucks
Sarah Read 45
Jesse Read (male) 15
John Read 11
Triphena Read 8
Ezra Read 5
None born in Bucks
They were living 3 doors away from John Brimley, 50, publican, also not born in Bucks
Could Jesse be Josiah?**
David
** Nah! Don't think so. All that member submitted dross has a Jesse as well born 1827. As he wasn't with parents in 1841 the only way to confirm Josiah is to check the parish register film