I'm sure by now you have done a good deal of research into Henry STYMAN.
He married Violet Beatrice on 15th Feb 1921 (#4332) and their first son arrived about 3rd Sept 1921.
Ronald Frederick.
I am checking to make sure you have seen this man's WW2 service record which has a photo of him.
As half brother to your lady, you can look for familial likenesses.
Sue