I am trying to find information on my great grandfather, Patrick Jordan and his family. I have only the following information:

Date of birth: either 17 Nov 1853 (from his US Navy enlistment records)or 19 Apr 1854 (death certificate)

Father: John Jordan. Mother: Nancy Mohn (both from Patrick's death certificate.) His enlistment papers notes that a parent was still living in 1880.
His obituary states that he was from County Monaghan and that he immigrated to the states at the age of 15 (with or without his parents?)

Any help would be greatly appreciated!