Hi Julierose,
1841 census Muthill Village Perthshire
Agness Erskine age 9
Ann Erskine age 35
Christina Eskine age 7
Martha Erskine age 9 months
(all born Perthsire,Scotland)
James Erskine age 30 born Scotland Occupation:Blacksmith
No sign of your Beatrice.

1851 census Benniebeg,Perthshire
Ann Erskine 50years
Ann Erskine age 15 years
Martha Erskine age 10 years
(all born Muthill,Perthshire)
James Erskine age 42 born Edinburgh,Scotland Occup: Blacksmith
Sorry I can't help you with birth details for James or Ann but found the following in Victorian records,
which might help you.
ANN ERSKINE (born Perth) died 1857 Reg #4801
Father: Duncan Ferguson Mother: Not stated
ANNE ERSKINS m GEORGE CAIN 1858 Reg #811
They had 11 children

ANN CAIN died 1897 62 years Geelong Hosp Reg #5265
Father: Jas Erskine Mother: Ann Ferguson
CHRISTINA ERSKINE married WILLIAM COSSER 1865 Reg #1865
Don't see any children for them
CTINA COSSER died 1907 Fitz N 73 years Reg #12122
Father: Jas Erskine Mother: Ann Ferguson
MARTHA ERSKINE married WILLIAM WILSON 1859 Reg #4363
They had 11 children

MARTHA WILSON died 1911 Fitz N 70years Reg #4856
Father: Jas Erskine Mother: Ann Ferguson
I have details of the 22 children if you want them.
Only death I could see for a James that fitted the age was -
JAS ERSKINE died 80 years 1887 Cmaine (Castlemaine) Reg #13054
No parents listed.
Did he come to Australia with the family?
Good luck
Raylen