Adopting a teenager in your 20's?

My brother is 24 and him and his girlfriend are thinking about adopting a teenage boy between ages 12-16 because she read in an article about teenagers not getting adopted and end up living criminal lives after leaving foster care and that motivated both of them to take a stand. He already has a son that is 5 months old but he always wanted a son that be cold kick around the football with. I don't know what to think about all this thats why I came to you guys. What do you guys think ? Should he go through with it ? Do you feel he's to young ?