i THINK maybe this was the Aunt as it also mentions the names you posted, so maybe you could track your Mums family from them? so could be your grandfathers brother
always worth when that stuck to search other family and see if it leads you back
scotland census 1901
Donald McLeod 43 (born Lochs, Rossshire)
Kate MacLeod 36
Jean A MacLeod 13
Kathie M MacLeod 11
Donald S MacLeod 11
Murdo MacLeod 10
Lizzie J MacLeod 8
Hector J MacLeod 6
Ishbel MacLeod 4
Barabel MacLeod 2
Norman MacLeod 1
Margaret MacLeod 1
if you then look at some earlier census for Donald born c1858 there are a few options,
maybe if you can find the marriage of Donald and Kate it will shed some light on your Gt Grandparents
ps
looking further, it looks like some one Ancestry has them on a tree, you may already have been in touch or seen this
apology if so, IF it is the same ones then Kate is Kate Webster Rodger,
if their tree is connected then doesn't look like Donald is your Grandfathers brother, but maybe worth contacting if you have not already done so, sorry not to clued up on the areas in Scotland so i may be way off?