Given that no relationships are stated on the 1841 census, it's possible that this is more than one generation of a family especially as Margaret is enumerated as 55, so really 55-60 and Maria is 6 months.
There are entries for some of the family members in IGI extracted batch C112555 for Dunnottar
Alexander born 26/5/1814 son of Robert Milne & Margaret Grieve
Mary born 17/9/1822 baptised 4/10/1822 same parents
Robert born 31/7/1825 bp 18/8/1825 same parents
also these who aren't with the family in 1841
George born 21/3/1828, bp 18/4/1828
David born 24/5/1821, bp 9/6/1821
Robert Milne married Margaret Grieve 27/11/1809 Kinneff & Catterline batch M112624
possible baptism for Amelia in Dunnottar batch C112555
Amelia bp 18/4/1837 dau of Robert Carnegie & Jane Milne
