I received a message in Geni.com dated 13 August 2012 but I only read it tonight. The message was from Iszham Idris, whose granduncles were brothers Mohd Arshad bin Osman and Dr Mustapha bin Osman.
Iszham Idris also provided a family photo of Dr Mustapha bin Osman, which he obtained from his aunt, Aishah bt Mohd Arshad. I downloaded the photo from BOX tonight. It had Dr Mustapha bin Osman, his wife and daughter, posing outside a brick building, in the sunshine. The photo was taken in London. No other information was provided; the photo was undated and the occasion unknown.
Dr Mustapha bin Osman graduated from Hong Kong University in 1924. Dr Mustapha returned to Malaya in 1931. I would guess the photo was taken after 1924 and circa 1931, before WWII (1941). He served in the Japanese administration during the Japanese occupation in Malaya. Nothing is mentioned about his family (wife and children) during the war. Only his siblings were mentioned - they held posts in the Japanese administration during the war. He was in charge of the Lady Templer Hospital in Kuala Lumpur in 1952. It is not known how many times he returned to London.
His date of marriage is unknown but I had guessed a date from other sources. If he got married circa 1924, then the daughter would be at least 6 years old in the photo, but she looked older than age 6. If he got married circa 1931, then the daughter would be approx. 10 years old at the break of WWII (1941).
His daughter was already a big girl in the photo, probably around 10-12 years old. It is not known where and when his daughter was born, so it is difficult to date the photo. The photo was probably between 1935 and WWII (1941). That's my best guess.