Roby,
It appears that all De Mamiel's descend from Captain Henri HOENER/HAENER (1802 - 1866) of France who married firstly Anna Maria Caroline SWIFT (1804 - 1849) of Ireland and secondly Sarah Emma MacDERMOTT (1816 - 1882). Upon Henri's marriage to Anna Maria Caroline in Brighton ENGLAND in1833 he listed his surname as HOENER/HAENER de MAMIEL. His father had married twice and his mothers maiden name was MAMIEL. From this point the couple used DE MAMIEL as their surname and all 7 children ( and 3 from second marriage) were given the surname DE MAMIEL. The boys all seem to have HOENER as their last christian name. After the birth of their fist son in Belgium, HEnri & Anna moved to her families property in Ireland.
Would the Thomas DE MAMIEL you mention be Thomas Gordon Charles Hoener DE MAMIEL? He was born in county Meath about 1845 and emigrated to Australia by 1863. If so this would make your gg Aunt Catherine ROBESON. This couple are my great great grandparents!
Are you able to share anything about the Robeson's?
HellyMelly