Many thanks for the additional information.
I got a bit confused over Frances's post, but I hope I have understood it the right way.

I had found a John Sheard bn Bradford m Grace Sugden had a son John. I think the detail that threw me, was the source saying the John bn Ovenden was presumed to be the elder John's son.

So if I have read your post correctly, it seems like the John Sheard from Ovenden, didn't settle on the Island. It was in fact John and Grace's son, John.

The info about David was handy, as we had been trying to work out where a David bn c1825 in England tied in, though this may not be the same David. I did find that a David Sugden Sheard was born in Bradford 1805, so it's possible that David bn c1825 was his son.

Please correct me if I have misunderstood anything. Thanks again.