~ thinking this might be Alexander in 1871 at his grandparents, with mother Margaret (transcribed as Harrie on the index I am looking at):
James Harrie 61 Hand Loom Weaver b Poulton, Kincardineshire
Elizabeth Harrie 57 b. Marykirk, Kincardineshire
Margaret Harrie 22 b. Montrose
Alexander Harrie 20 b. Montrose
Edward Harrie 17 b. Montrose
Alexander Harrie 3 grandons b. Montrose
Address: Townhead, MontroseJames Harris and Elizabeth Moir are given as parents to Margaret in the a/try tree mentioned.
Another illegitimate child given for Margaret Harris is Edward b. 1871
https://familysearch.org/ark:/61903/1:1:XYTN-BZR... also seems to be registered in Dundee
https://familysearch.org/ark:/61903/1:1:XY1X-C8Y Sometimes happens when birth took place away from parent(s) normal residence and registrars passed on info to the locality of parent(s) residence.
Monica
PS: Someone has posted this info
https://familysearch.org/pal:/MM9.2.1/S5MN-2SL Maybe Edward died young?