Although it's known that Thomas was born in Soloheadbeg to a father named John Treacy and a a mother named Mary, we're unable to say for definite that he was a son of John Treacy and Mary Looby who married in February 1818. If he was indeed a son of John Treacy and Mary Looby, then he was born in November 1821 because a record of his baptism (on 8 November 1821) has been located (sponsors were John Hanley and Winifred Connors). Unfortunately this birth date doesn't tie in with the age given on his marriage certificate from February 1873, which looks like 37 (indicating he was born around 1835), but the age on the certificate is difficult to make out and could also be deciphered 50 or 51 (indicating he was born around 1822 - a nice fit with the baptismal certificate). However Thomas's death certificate from December 1895 gives his age at 54, indicating he was born around 1841.
It's known that our Thomas had a brother named Denis. Unfortunately no baptismal record for a Denis Treacy born in Soloheadbeg to a father named John and a mother named Mary was located.
At the time of his marriage, in 1873, Thomas's occupation was a farmer (according to his marriage certificate). At the time of the birth of his son, Thomas, in 1881, he was the superintendant of a coal yard (according to the birth certificate), and at the time of his death in 1895, he was a labourer.
Interestingly, among the all the sponsors at the baptism of Thomas's and Mary's children, there's not a single Treacy; the sponsors are mostly Carews.