Hi, i was reading your post and noticed that a magority of what you have written i have in my family tree book. It says that Maurice Mannix & Margaret Dowd had only 1 son (that is known) by the name of James Mannix b. 1834 County Kerry, Ireland d.25 Nov 1909. He married Johanna Finnaughty had 15 children. Margaret, Mary, Maurice, Ellen, Michael, Annie, James, Patrick, Bridget, Thomas, Sarah, Catherine, Julia, John & Dennis.
James & Johanna, originally from Firies Cross Co Kerry, Ireland, left liverpool in 1863. I hope this was helpful & i would love to know anything else that you do.