Ruperts sibling

[Christine88]

Baby number 2 due in 8 weeks, another boy! No name ideas yet!

Henry
Oscar
Edward
Tobias
Hugo

Caspar!

Alistair
Arthur
Edmund
Charles
Lucian
Timothy

Marcus, Alexander, Piers, Giles, William?

Arlo
Samuel
Jonah

First thought was Dexter.

Please be aware if you do call your ds Giles,some people will assume your a Buffy fan as there is a character called Rupert Giles.

Rupert and Henry or Rupert and Theodore

Monty

Felix
Edgar
James
Jackson

Algernon

Miles
Crispin
Elliot
Barnaby

Guy
Lucas
Edwin
Frederick
Benedict

Sebastian
Sylvester
Merrick
Dante

Actually I think I have to scrap Barnaby - you need to be careful of ending up with a bear theme!

Arlo

Tarquin
Caspian
Rufus
Jonty
Miles
Hector

Tim & Simon (true live brothers to a Rupert. In their 50s now. The other Rupert I know doesn't have any siblings (also 50s).

The one I know had a brother called Oscar.

Jasper
James
Hugo
William
Frazer

Love Caspar as already suggested

Also like:
Theo
Arthur
William
Alfred
Nico
Luka
Milo
Asa
Louis

Jasper

Edward

Miles

Bertrand (Bertie)

Alistair

Freddie

William

Hugh

Max

Toby / Tobias
Gregor / Gregory
Alexander
Elliott
Edmund
Max..
Michael
Christopher

Some good ideas here. Oscar fits especially well, and Edward, Max, Henry and James would be good choices.

I think you should go for 1 or 2 syllables.

Reuben (if the similarity of the opening sound didn't bother you)?
George?
Adam?

Would you go double R? Rupert and Ralph?

Conrad
Ambrose
Anthony