I would like to correct my earliest information. I had only family recall of "Butler cousins", which led me to conclude Thomas Butler was a brother of Richard.
Church records in Gortnahoe, Co. Tipperary located baptismal record for Thomas, the son of Thomas Butler and Margaret Danniel/Donnell/O'Donnell. Thos. & Margaret were married in parish in 1826. They had 3 sons baptized in parish. Thomas Feb 25, 1827. Ned baptized Jan 1829, and Michael baptized May 1837. On each of these 4 church records, Margaret's surname is spelled differently. The Tipperary Heritage Center feels confident it is O'Donnell.
Interested in hearing from O'Donnell researchers in Gortnahoe area. Thanks.