A riddle question number 2

When you were 2 years old, your brothers's age was $2 \times 0.5= 1$

So your brother is 1 year younger than you.

Hence now you are 100 years old, your brother's age is $100 - 1 =\boxed{99}$ years old.

half of 2 is 1, and so that means your brother is 1 year younger than you

When I was 2 years old my brother was half my age which meant he was 1 years old. When I am 100 years old then my brother would be a year younger than me which means that he would be 99 years old.