Searching for info on Timothy Sheehan b. 1823 Whitechurch, Cork

I am searching for any and all information on my g-g-grandfather, Timothy Sheehan (b.1823) who emigrated from Whitechurch, County Cork to the U.S.A.  I have a record of a Timothy Sheehan who was on the ship Marmion that transited from Liverpool and arrived at Castle Garden immigration center in New York City on 3 October 1848, but I am unsure if this is indeed my ancestor.  Timothy married a Johannah Toomey (b. 1826), also from Ireland, and eventually settled in Shenandoah, Pennsylvania where he worked in the coal mines. He is rumored to have had a brother, Andrew, who was a blacksmith and also emigrated to the U.S.A. and settled in Texas.