I have a lot of info on I.S.Soden and J.F.Soden,including photographs should you find that they are the ones that you are looking for. They are remembered on Winchcombe war memorial., Gloucestershire. Schooling was in Suffolk so I’m not sure there is a connection with your Charles. There was a third brother who died of Blackwater Fever in Burma during WW2 but his name escapes me at the moment. Their father was the local GP in Winchcombe.
PM me if you need further info.

Regards