In the June 6 1841 census ages were rounded down to the nearest 5 years. Thus Ann and Joseph, whose ages were given as 20, could have been born between June 7 1816 and June 6 1821.
The ages given were pretty erratic for this couple,
35 for both in 1861, 58 & 57 in 1871 and 66 for both in 1881. At the extreme, Ann could have been born in 1813 or 1814.
There is an Ann Quirk, christened in Patrick on June 19 1814, who might be worth investigating. Her parents were John Sayle and Catherine Quirk