Barretts in Cork

Lookinf for info on William Barrett born in Cork around 1821-1825. Not sure what part of Cork he was born in. He married Margaret Lahane from Bandon. They had 11 children. Some are on ancestry and some I found by searching ship manifests coming to Boston. One of his sons--Thomas born in 1872 in Bandon--marrried a Margaret Holland  from Innishannon and had a number of children in Ireland--before moving to Boston in 1906-1907.

The 1901 census has William (Thomas's father) living with Thomas and his family in this town of Innishannon. I belive that William died around 1902. I am trying to find out who were the parents of William and where was he born. His children with Margaret are as follows.

Margaret 1858

Mary-1859

Ellen-1861

John -1863 (my great grandfather)

Richard and Denis-1865--twins

Joanna-1866

William-1868

Thomas -1872 *****

Catherine-1873

Elizabeth -1877

*****Thomas married a Margaret Holland of Innishannon and had 3 children--Margaret, William and Julia. Margaret Holland's mother was Julia Holland and her father was Jeremiah Holland.

So looking for where William Barrett (1821--1825),the father,  of all these children came from,and who his parents were?