Chris, I've got a big chunk a Keig tree, which I researched for a lady in Canada. William and Ellen (Nellie) were the children of William (born Ballaugh IoM c1843) and presumably Anna Taylor who I was told he married in NZ c1865.

The Elizabeth he married was almost certainly his cousin, not his aunt. William (b c1843) was the 8th child of John Keig born c1804 (baptised Jurby 1804). John had 4 brothers, all of which disappear from the Manx censuses at various points. Any of these could have had a daughter Elizabeth.

David