Arthur's brother should be called....

[ChittyBB]

Wilfred (nn Fred)
Hector
Max
Fergus
Thomas
Samuel (nn Sam)
Jack (family name)
Lawrence
Humphrey (I love this but don't really have the guts to use it)
Byron (family name but I'm just not sure that it isn't cheesy)

Of your choices I like Samuel, Lawrence and Wilfred.

You could get Bertie from Cuthbert or Albert.

Other ideas are:

Edwin
Monty
Harold

Wilfred, Hector or Lawrence.

Hal could also be short for Hallam.

Harold is wonderful! I wonder whether DH would agree.

Harold and Arthur are both ancient English names.

And Harold could be Hal don't you think.

Hal and Artie.

Just thought of Shipman :-(

Wilfred (nn Wilf rather than Fred I think) as that's what we're planning to call our son due in a few weeks! Love the name Arthur but we couldn't use it. Edwin was close second.

I like Byron too.

Bentley (Ben)

Harold to Hal is fine.

Arthur was Henry VIii's older brother, which I would find cool if I was an Arthur -Henry pair but you might not!

I wouldn't let Shipman put you off, unless that's your surname!

Haldane?

Max. Definitely Max.

Don't let Shipman put you off. It's not the first thing that comes to mind and that will be even less so for your DS's generation.

And those 'old men' names belonged to young men at some point which rich and diverse lives. Many of whom gave their life for us 70 odd years ago so IMO there's nothing 'ugly' about them.

Random

Edward

Jack

DH has vetoed Harold :-(

He likes Jack but I think it might be a bit plain next to Arthur.

Percy
Stanley
Reggie
Albert
Rupert

Wilfred from your list but Albert nn Bertie works well.

Arthur an English name ? wasn't he fighting the English ?

I think John would go really well.

Francis
Edmund
Edwin
Magnus

Magnus is awesome

Ralph! (My grandfather was Ralph Arthur)

Lawrence. (or Laurence).

OP, I usually word-associate all the time and Shipman never crossed my mind in terms of Harold! (Primrose as a name choice would bring up Shipman, fleetingly, to me though however).

As PP suggested

Edmund (nn Ned, if not in Scotland)
Gregory
Edgar
Percival

Hugo
Heath
Gilbert
Herb(ie.)(ert)