Yes Joseph had a sisters Jane,Hannah,Rebecka and Ann,his brothers was Benjamin (my 3x grt grandad) and John,they was all born in Coaley which is not far from Dursley.the Ford family was big in Coaley and Uley for over hundred years,i have spoke to a few people who are related through my Ford family from Coaley,and i have spoke to people with Ford family from Coaley working with my Ford family but not have found out how they are related,theres lots of gaps in the records.As soon as we can find your Sarah parents we can go back futher,i have some Gloucestershire records on cd.
If you can find the aussie marriage records that might give you her parents.i see she named her first daughter Elizabeth,might be a clue,in those days the first kids got there parents / granparents names.