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Well, if you're still working on this idea, figure out your story's specific time line. If you plan on having it literally span 20+ years of the characters lives try to figure out which major events would directly or indirectly affect their lives.

Now, I don't know anything about Malaysian history but say a major city is evacuated during the time period, do they have to move, or is their hometown somewhere that would take refugees?

If there's a war, are they drafted when they reach a certain age or is a family member drafted in their youth? Are they killed in the war or do they return home?

I think you may want to do some more research, and establish the background a bit more.

Who's running the country?
Who's in charge once Malaysia is independent?
What are the laws, especially restrictive ones, that govern their life?
How is the caste or class system? Are your characters poor, middle class or upper class? Are they servants?
What are job opportunities like?
Do the different races interact often? Are they allowed to?