My McCarthy Line?

Am looking for any help in identifying my McCarthy line. My 1stGgrandfather, Francis McCarthy was born abt 1859 in Cork. Family stories say our line comes from the Ballyhooly area. I know nothing about the family in Ireland. What I do know is Francis "Frank" came to the US abt 1880 to NY city where he worked as a horseshoer until his death in Oct, 1900 at the age of 41. While here he met and married Margaret Griffin, who was born in Killeagh/Youghal area. All I know abt her is she was born abt.1872/1875 and came over here to NY 1890-92, She married twice. Frank abt 1892 and had my grandfather, Richard Francis McCarthy(b. 1895) and again 1901-02 and had a second child, Frederick C. Miller(b.1903). She was widowed again abt 1905 and returned to Ireland with both boys in 1905-06. Her father's name was Richard Griffin and no mother is named on her death certificate. Frank's death record states his parents names as Martin and Bridget/Ireland. I do not know how accurate this may be as Margaret was 13-15 years younger than Frank and he had been away from Ireland along time.

There is no 1911 census record so far showing where my grandfather, Richard McCarthy and my 1stGgrandmother, Margaret were living in Ireland. My granduncle Fred Miller(age8) is in the 1911 census living with Mary and William Wall in Knocknamaderee, Killathy. Mary Wall is also in the 1901 census with her first husband, Maurice McCarthy and their children, Jeremiah, Ellen,John, Margaret and Mary. All these children minus John and with the addition of a Richard Wall(age5) are in the 1911 Mary and William Wall census record. I would like to find out if Maurice was Frank's brother? Was Mary ,Margaret Griffin's sister or sister in law? Are there any records of a Martin and Bridget McCarthy? Did Frank have any other brothers or sisters?  My only US living McCarthy relative has been to Ireland and has had contact with a distant relative Jude Cleary(we cannot reach her right now)who is connected to us through her mother(a Peg McCarthy). Her father, I believe would need to be a McCarthy. Could it be this Margaret (?Peg) McCarthy is Maurice's daughter? Not sure. When she visited Ireland, this distant relative took my aunt to Killathy Cemetery and showed her 3? grave stones and told my aunt " these are our relatives.."...all men I think. Not Sure. In November, 1920, my 1stGgrandmother, Margaret Griffin McCarthy Miller returned to the US with Fred(age 18). Her passenger record states her passage was paid by her "sister M. Wall".  Could two sisters have married two brothers?  Any help re: these questions would be greatly appreciated. Thanks Kathy