If you look at iomfhs.co and see the birth index in the research section you will see Constance is the daughter of Moses Canning and Jane Killip. There are other family names to be seen.
Moses married Mary 1891.
It looks like Peter Alexander Michael Strappini married Elizabeth Radcliffe in London 1871. He may have had a previous marriage with children, one of which appears to have joined the church and lived in Guernsey.
1891 census in Douglas:-
Peter Strappini 65 Barrister in Law London
Elizabeth 50 Isle of Man
Elizabeth C. Cannan adopted Douglas
The Cannan name came from Thomas Cannan, father of Moses.