My great grandmother was Bridget Crosby Dolan. Her sisters were Ann Crosby McGovern, Rosanna Crosby and Susan Crosby Lanahan. When Ann McGovern died a Michael and Ann Lanahan were taking care of the nieces and nephews. Michael had to be Ann's brother-in-law. When Bridget Crosby and James Dolan were married 1853 Ann Crosby McGovern was the witness (Maid of Honor). Also, Ann was Michael Dolan (1854) and Elizabeth Dolan 1865 sponsors at Baptism. Susan Crosby and Peter McGovern was Helen Dolan(1861) sponsor at Baptism. Michael Lanahan was Sara Dolan (1870) sponsor at Baptism. These records were obtained from St. Michael's Church in Philadelphia and St. Charles archives.
Rosa Crosby was Rosanna McGovern's (1860) sponsor at Baptism. .Susan Crosby was John McGovern (1858) sponsor at Baptism. Margaret Lanahan (age 4 in1871) Rose Crosby (age 94 in 1912) and Annie Sellers (age 1 in 1890) were buried in the McGovern section at the cemetery. Their son Peter McGovern married June Carlin.
Michael Lanahan married Ann Reed in 1867. He must have been Patrick Lanahan's brother. When Elizabeth Dolan (Bridget's daughter) was married she listed her mother's maiden name as Lahahan. Since there seems to be a connections between all the family members it is possible Susan, Ann, Rose and Bridget's grandmother name was Lanahan and she married a Crosby. There was a Ann Lanahan that was Henry's sponsor and a James Dolan was Mary Blanche' sponsor.
I have records on all of the families and I am in contact with South Mayo Historical Society.
I hope that this information is helpful to you Jack Gerst