Thanks to all, the great answers are very welcome but most fall into the marriage, birth and census details I have in my own files.
I conclude Michael Fitzgerald and his wife Ellen Winn (Wynne) were born about 1829 (Ireland) and 1830 (not sure where) respectively. The 1861 census shows them with son Thomas Fitzgerald and daughter Bridget but Michael appears to have died before 1871. The census of 1871 shows Ellen as a widow with her son Thomas and daughter Bridget Fitzgerald as members of Bolton Union Workhouse. Ellen's father is Bartholomew Winn (Wynne), an unusual name, that I found resident in Bolton, perhaps she went back to her roots after the demise of her husband.
When Thomas Fitzgerald reaches adulthood he is back in Liverpool as an Iron Molder married to Mary Mccrink. Oddly not one of his 7 sons is named after his father Michael and none of his 6 daughters named after his mother Bridget.
Here are the sons names and approx year of birth:
William, 1885 joined australian forces at Keswick discharged
Thomas, 1885 joined Otago regt NZL died in action circa 1916
Herbert, 1890 joined Kings Liverpool Regt died in action circa 1916
Austin (augustine), 1895 joined Canadian army circa 1916 survived
John, 1904 (my grandad)
I can make a case for a few "Michaels" as suggested in the replies but can't make a definitive link the 3 or 4 bros thing would be a clincher if i could find such a family.
I've tried searching Irish records combining Michael's birth year with a presumption his father might be called Thomas but nothing jumps out.
Love to find out what part of Ireland Michael come from.