There is an Agnes Richmond aged 15 employed as a female servant at Low Armsheugh ( a farm I suspect) in Irvine on 1841 Census. ( Her age may have been rounded down as many were on the 1841)
James and Agnes Wyllie ( spelt with 2 L's) are at Cotton Row, Irvine on the 1851 Census - Agnes's place of birth is Symington, Ayrshire. Agnes is recorded as 27 years old. James is 40.
William Owens is aged 11 at Kilmaurs on 1851 Census but in fact he is living at the village of Crosshouse in Kilmaurs Parish.
This means Agnes could have been around 15/16 years old when she gave birth.
Looby