+1 to the above. Have a backup plan if you decide to add more. When you say "teenager" how are you defining that time frame? These fish look small to me based on the pics. Maybe the body size of a quarter? If this is accurate, you should be able to add more about the same size with little problem. Angels are a schooling fish which can explain why your 2 stay together. When one adds to a collection, the fish have a hierarchy that they establish so some squabbles do occur but are usually short lived. This would not be the reason to not add to the school. Lastly, to me, these both look more like females than male & female. I'm using the finnage from the Black one but there appears to be the outer edge of the ovipositor (a.k.a. Papillia, breeding tube) which looks more blunt than pointed on the other fish which would also be a female. These are both only hunches as the only guaranteed way to sex Angels is when they are spawning. The female is the one laying the eggs
lol Hope this helps