Hi, I can help with this as I have extensively researched this family (my Mother was a direct descendant. There is also an interesting story around this.
The parents of John were John Fortescue 1808-1861and Rebecca Howe 1809-1906. John was born in Papplewick, a small village in Sherwood Forest. His parents were John Fortescue 1786-1854 and Elizabeth Hopewell 1783-1859. They married in Papplewick in 1805.
This is where it gets interesting as John was born in Marylebone London. It seemed a bit odd that a young man who was poor should find himself in such a small place so far away from where he was born. I must stress I have no sources for the next bit but what I do have is compelling. If you google Marylebone and Papplewick you will see that the mill owners in the latter had an agreement with the poor house in Marylebone to supply child labour for their mills. I believe that’s how John came to be there and incidentally found the Fortescue name in Nottinghamshire.
I managed to establish his parents names but at that point hit a brick wall. The likely link to the Fortescues with the money and titles etc is I am afraid lost to history!
If you would like any further help around this branch of the Fortescues, please let me know.
Ian