I am descended from Sidonia Trudgain (Trudgeon) b. 1816 from St Mewan who is the elder sister of the Joseph Trudgeon you mention, b. 1824. Their parents are our ancestors in common, Joseph & Dorothy (Mitchell) Trudgain. Dorothy's parents are Richard & Elizabeth.
Sidonia married Richard Hancock in 1839 and they had at least 5 children, all born in St Austell.
From census information I've got details of Sidonia's siblings and more on some of their own families:
Mary 1819 Elizabeth 1821 Joseph 1824 Richard Mitchell 1826 Harriet 1829 Catherine 1833 William & John (twins) 1835 Thomas 1839
I'm sure I've missed some so would like to swap info with others in the family.