Why Brontё?

Hi!
Could you please kindly explain to me why this famous name is always been written with ё?

Does it tell anything about the source of of this second name?
Or should it be spoken in some special manner? Like Брантё?
Or is it caused by some ancient grammar rules and should be written so?

Simply why Bront

Probably affectation. The father of the famous Bront

That's was a very interesting answer!
Thank you!