they are very likely Thos + elinor costain with family:
CATHNE 06 SEP 1801
JANE 26 JAN 1803
JANE 21 FEB 1815
WM 15 SEP 1805
ELINR 24 AUG 1806
WILLIAM 05 AUG 1820

it is possible that Thomas is child of Henry Quilliam + Isabel Cubon family:
THOMAS 26 JUN 1770
THOMAS OCT 1775
MARGT 01 MAY 1773

Henry Quilliam is first Quilliam to leave a will in Arbory (parish records are missing for a period) thus looks as if he moved from Malew where name Henry is found in several families

Cubbon and Costain are old Arbory names