Greathead bible

A while ago I was sent a copy of a page of a bible containing details of the children of William Mawer and Jane Greathead. At the top of the page were entries about Robert and Esther Greathead. At the time I could not manage to understand how the families were related. I was sure they should be.

I write now because I have been reviewing some of my old data and believe it or not still cannot find the relationship, but there must be. Any ideas?