On my mother's side, Michael McKeon and his brother, Thomas, served in the 25th; a g... uncle on my paternal line did as well. For this sort of research the Massachusetts Military Museum & Archives, located in the "Armory" at Lincoln Sq. is an invaluable source of information. They were able to help me learn about the unit and its members. The folks there are very friendly to researchers.
The O'Neil's that Merski mentioned in her post are a very interesting lot. Four of the brothers served in the 25th; the fifth served in another regt. For years after the war, former soldiers' obits often contained a line about having served in the 25th, E Co. under Captain Tom O'Neil. He was a "Deep Sea Diver" before the war (1860 census); he died from wounds rec. at Cold Harbor Va. on June 4, 1864. One brother, Lt. James, survived the war, and later spent many years away from Worcester (He worked as a fencing [and more?] instructor in the New York Athletic Club.) and his religion. He returned to both before he died. Both of them were boxers, and it's said that there was a match (demonstration of the art) between them on Thanksgiving Day, 1863. I am sure the other brothers that served (John, Arthur, & Charles) have their own stories, but one of my favorites is of the sister, Kate (married Owen Kane) that traveled from Worcester to visit a wounded brother. Her travel companion, if I remember correctly, was none other than her sister Annie's husband Richard O'Flynn. He that would become the Worcester book-seller and amateur Irish-in-Worcester historian.
Thomas and James had experience within military organizations before the Civil War. On Aug 3rd 1852 some adopted citizens of Worcester met at Fenwick Hall to discuss the formation of a military organization. The purpose of this militia would be to uphold the laws of and the constitution of the United States and to be ready at all times to sympathize with the suffering and oppressed people of Ireland. The first meeting was held, Aug 9th 1852, in the "Catholic Institute" on Temple St. Officers were elected. (Forgive the lack of quotation marks: I am pretty sure this is close to how O'Flynn relates the story.) This militia was the Jacksonian Guards, they were disbanded, along with other "clannish" militia, by the governor not many years later. The Emmet Guards followed after a few years, and that is the unit the O'Neil boys joined.
Their father, Charles, wrote two books. I have read the published The Military Adventures of Charles O'Neil and hope to see the unpublished The Life and Times of Charles O'Neil. The last time the book was seen it was in the possesion of Mrs Margret Murphy. In The Military Adventures... Charles reveals the fact that his generation of fighting O'Neil brothers saw a bit of action. Charles's brother, Arthur, enlisted in 1804 and was assigned to the seventy-four gunship Terrible, under Nelson. A few months later he was killed in an engagement between British and French forces off the coast of Holland. Another of Charles's brothers, John, was killed at Trafalgar in October of 1805. Their brother James served two years and seven months. James was with Sir John Moore on his retreat in December 1808, and was killed in the battle of Talvera in July of 1809. Charles, after a few enlistments and a couple of desertions, served eight years in an English uniform. In 1811 he received 300 lashes for refusing to attend Church of England religious services. He served during the Peninsular War, Continental Campaigns, fought in the bloody battle of Barossa, the siege of Badajos, and was twice wounded at Waterloo. He received an honorable discharge in 1818. (I don't think there are any direct quotes in there, but I hereby cite Charles O'Neil and Richard O'Flynn.)
another long one, John