Which one is correct:

>1)Unfortunately they are not **at** the same age so I can't expect them to behave in the same way.

>2)Unfortunately they are not the same age so I can't expect them to behave in the same way.

  I know that when we only want to talk about people's age we say they're the same age or they're not the same age but what about this sentence,I want to emphasize both about the age and the fact that people behave differently at different ages.

Thank you in advance for your help