Well, I can see Stewart's and O'Brien's but nothing that immediately jumps out as being these two chaps.
I think you need to ask your mother a couple of key things to make progress with this-
- does she remember if they were Army, Navy, RAF, Merchant Navy or indeed civilians?
- were they killed "away at war" somewhere or in the UK or more specifically Belfast? (did notice a few Belfast burials when looking at O'Briens & Stewarts, by implication meaning they died there)
- Any clue if this was early, mid or late wartime?
If you prompt her with specific questions, you never know it might jog some memories!