It will depend on the dates and if the parish records for those years have survived.
Griffith Valuation was done in Galway in 1856:www.askaboutireland.ie
Christopher Usher, Parish of Killallaghtan, Townland Eastwell
Poor Law Union Ballinasloe (pt of) OWNS THE LAND
22a house, outbuildings and land 513 acres 3 roods 10 perches
22b herd's house and outbuildings
Thomas Usher, info same, tenant of Christopher Usher
#20 house and land 2.0.16 and
#21 land 3.1.39
Christopher Usher, Parish of Killallaghtan, T.L. Doonaree
tenant of Lord Clonbrock
#11 land 38.1.37
No Byran's in the Parish of Killallaghtan, but 39 Byran's in other Parish's, probably close by.
Galway is divided into East and West genealogically but both belong to an Irish History Foundation with parish baptism and marriage records. It depends how early you need to search as very early records might not exist. You can search for a marriage as you have both names, and also for children with both parents names. You wouldn't need a year as when you have both names you don't need it.
A marriage record will have both their father's names.