I Am Searching for the Mother of Mary Ann Roberts Who was Born IN the

I am searching for the mother of Mary Ann Roberts who was born in the colony Australia in 1792, as there is no records of Mary Ann`s birth only her marriage to a Richard Lewis who arrived in Australia as a convict on the Coramandel in 1802 and who helped to discover Bathurst Plains in 1814 with Evans he died in 1828, buried in Holy trinity cementery Kelso NSW.
Mary Ann & Richard had twin boys richard & james 1810
Mary Ann 1812
Henry 1814
Louisa 1817 Married James Smith 1833
William 1820
Elizabeth E 1825

Mary Ann died in 1868 Sydney NSW.

Her second marriage in 1829 to James Evans.
Mary Ann & James had three sons James, John & Edward.