Fictional heroes and heroines are usually an amalgamation of physical and character traits observed in several people.In addition, they are set up to endure as much agony as the author can pile on right through the novel. The reader must feel satisfied at the end of the story that both hero and heroine have learned something and are better people because of it.
All well and good. However, many writers need a real life person to focus on as they create and develop their hero and heroine. Regency set stories require a dashing gentleman, tall, muscled, elegant, sporty and suave. Other qualities as per story requirement - possibly a tortured soul...certainly a crack shot or a skilled swordsman...
It helps to have a visual stimulus - very often several models are used to achieve a complete hero. Hence, writers work extra hard; spending many hours poring over pictures to fuel their imagination. They seem to prefer black hair, so the following possible beaux are all dark [personally I think David Wenham and Sean Bean could also feature as Regency characters.]
This is a small selection ... but tempting.
All these heroes need their heroines.