Mary Anne Egan or Aegan

This is my great-grandmother.  Her brother's named John Egan.  Their father was Pat Egan.  He did not go by Patrick on any legal documents that I could find, and Mary's on death certificate, he listed as Pat.  John worked in a prison in Chicago, Illinois USA.  Cannot find a death date for him.

Never found a mention of Mary's Mother.

They immigrated during The Famine, 1851.  Do not know if she, John and Pat immigrated together.  At one point I found a John and Mary Egan in Dublin, but I have nothing to prove it was them.  Perhaps they sailed from there.