The ages of three friends: Anurag, Bhavik & Tarun are related to the diagram given below such that when just one digit is written in each box:

(1) a across is Anurag's age

(2) a down is the sum of Anurag's age and Bhavik's age

(3) b across is the sum of Anurag's age, Bhavik's age and Tarun's age

(4) Among Anurag, Bhavik and Tarun, we have a pair of twins.

All ages mentioned above are in years.

Using this data, determine the twins. Also, find out how many possible solutions are their for their ages and give one possible solution to their ages. Provide a detailed explanation along with your answer.