Upvote:2
I think this is probably a French army uniform of WWI (or soon after), for a couple of reasons.
Firstly, the number patches on the collar are distinctive of French army uniforms around this period. The number indicates what regiment the wearer belongs to; in this case, it's '30'. French Wikipedia suggests several potential regiments that this could be:
Secondly, the two medals also look like French decorations. From left to right (as we look at them):
Both these medals were awarded to members of allied armies (and civillians). However, given the collar patches, I'm pretty confident that this is a French uniform.
The OP says of their great grandmother:
she was born in 1874 and looked after the kids in the late 1890's before she got married in 1902. She kept up the friendship with the French family for many years after.
Given that this photo was taken after 1915, it could either be her former employer, or one of the children she looked after. Or it could be someone else entirely!