Hi Barbara,
I am the Parish Liaison for Shanagolden Parish (Ireland Reaching Out.)
I did some looking for you yesterday - census rcds and such - but the surname was too common, and there were a million Sheahans!
Then I got the idea to search for Clarence, thinking it would be an uncommon first name. BINGO!
There is a tree at Ancestry - The Strauss-Kingsbury Family Tree - and the owner is tracing your family. He also has a bit more info than you do. The owner, rkings3331, shows that Jerimiah Sheahan born 1748 and Mary Ragan 1792-1862 were the parents of James Sheahan b 1785 Shanagolden (died 1 Apr 1868 Lombard, Dupage Co, Illinois.) Jerimiah b 1748 and Mary Ragan b 1792 had 12 children according to this tree.
I see that the dates of birth for James do not match exactly your dates, but the names of the siblings do: Jeremiah b 1814; Mary b 1816; Morris b 1817; John J b 1818; Honorah b 1820; Mary b 1820; James b 1825; Daniel Sr. b 1827; Hannah b 1832; Catherine b 1834; Philip b 1837 and Patrick b 1838.
I suggest you view this tree and make contact with the owner. This tree appears to be very well sourced - obits, tombstone photo's, etc.
It is very difficult to get further back than about 1810 when conducting Irish research - there just aren't any rcds unless your family was gentry. That rkings3331 has been able to get back to 1748 is admirable!
By the way, I searched Ancestry.com family trees for Clarence Sheahan.There are MANY trees that show a Clarence Sheahan. I would suggest you conduct this same search, and invest some time checking these public trees out too.I'd be willing to guess you'll learn more details about your family.
Best wishes,
Patti Hacht
Lakeville, Michigan USA