Time has passed since this was originally posted, so pardon me if this has already been sorted. So Edward married in 1858 at Christchurch Church of Ireland, Derriaghy. Hugh married in March 1891 with his age given as 27. This would put Hugh's birth just before civil registration. A check of the Derriaghy baptismal register is best course of action. David married in 1903. Looks like there is a big discrepancy in his age in the 1901/11 census as it looks like he was born December 26, 1872. Thomas is born in 1876.
Derriaghy puts all their births into the Lisburn registrars district.