The biggest. All the Fiennes men are well endowed.
All they related?
Why is River Song posting on this thread?
Joseph & Ralph appear to average-sized (cut?) cocks based on the brief nude scenes they have done over the years.
Not much to go on so far.
Joe was the spectacular young sexy leading man to Gwyneth and Cate in 1998's two biggest films.
R5, he's on American Horror Story.
R5, he's still working, but in lower-profile projects. He played Merlin opposite James Purefoy, Eva Green & Jamie Campbell-Bower in the "Camelot" t.v. series a couple years ago and has been in several films.
He apparently doesn't want to be a Hollywood star. Got married and had a kid not long ago, too.
Btw, with regard to the OP's question, one of the people you could ask is Heather Graham. She was in a soft porn with Joseph about a decade ago. They had several sex scenes together and there are a lot of shots of his ass and maybe one of his cock if you watch closely enough.
What would you call it, R9?
When you do a B-movie that is an erotic drama with lots of sex scenes, that's often what it gets called.
It's called "Killing Me Softly" - here are some naked screencaps: