Question 886568
The difference in their ages will not change.  If they were two years apart three years ago, they're still two years apart, and will be for the rest of their lives.
If the sum will double in 10 years, then the difference will increase by 20 (ten years each).
The sum now is therefore 20. 
Brother A is 9 and Brother B is 11. (totals 20)
In 10 years, Brother A will be 19 and Brother B will be 21 (totals 40)