Who is older Amit or Naveen ?

Statement I : Naveen was born in the year 1990 and is 5 yr younger than Amit's brother.

Statement II : Amit is twice as old as his brother

If statement I and II together are needed to answer the question

Statement I only tells us that Naveen is 5 years younger than Amit's brother, but it doesn't give us any information about Amit's age relative to Naveen.

Statement II tells us that Amit is twice as old as his brother, but it doesn't tell us who is older, Naveen or Amit.

To determine who is older, we need to combine both statements. Since Naveen is 5 years younger than Amit's brother, and Amit is twice as old as his brother, we can conclude that Amit is older than Naveen.

Thus, it requires both statement I and II together to answer the question.