I took a look at the 1891 census you mentioned and see that Effie is listed a granddaughter
Henry 75, born England
Fanny, age 23, daughter, born ON
William, age 19, grandson, born ON
Effie, age 17, granddaughter, born ON
the 1881 censusis very faint in the image so there may be mistakes in the
indexed entry - it shows William as age10 and Effie as age 5. those ages are extremely faint and hard to read ? also cannot read the relationships but it does seem Effie would be a granddaughter.
Easter Ann 20
Since Effie is with Henry in 1881 and 1891 it may be her parents had died when she was small.
Catharine died Sept. 18, 1889 Kent - Henry died Oct. 18, 1898 Kent
There is an Anne Jane ALLDRED death March 18, 1876 Northumberland and Durham - she was age 23 and died of consumption - the informant was John ALLDRED
there is a notation on the record which says the deceased died in the Corporation of the township of Clarke and was wrongly entered
her parent's names are not shown
In Ontario birth records there is a William Alldred born Nov. 13, 1870 Durham Co. to John Alldred and Anne Jane Lowey
Wellington Alldred born Aug. 9, 1872 Durham to John Alldred and Anne Jane Lowry
but did not find Effie listed.
This seems to fit for 1871 census with surname mispelled which is not unusual.
1871NEWCASTLE, DURHAM WEST, ONTARIO
John, age 26, labourer, born ON
Ann Jane, age 19, born ON
William, age 5 months (Nov.) born ON
and then in 1861 again the family is listed as ALDRIDGE and parents are Henry and Catherine
1861 NEWCASTLE, DURHAM, ON
Henry, age 46, bricklayer, born England
Catharine, age 37, born Scotland
Hannah, age 19
John, age 17,
William, age 13,
Joel, age 10,
Mary, age 9,
Ben, age 6
Easter, age 4
Caroline, age 2
the children all born Upper Canada
so this matches with Effie being a granddaughter to Henry and Catherine and her father being John.
I have not found a death for John but it may be he remarried and the kids stayed with his parents?
I could not find Wellington in census or deaths?