I do have a listing of Donald McMillan's family of Cornwall Township, Stormont.
I'll have to dig it our and send info to you.
Hannah (sometimes noted as Sushannah) was also a daughter of Donald McMillan UE and Catherine McDonell. She married Donald McMillan of 24.4 Lochiel, Glengarry.
Sushannah's and Donald's youngest son Angus married a sister of one of my gr grandfather's also a McMillan. John McMillan who married Catherine McMillan (Donald's and catherine's daughter) was a first cousin to this same gr grandfather of mine.