After the babies' birth, a few days passed. A lot happened in these days. First, both babies' wings appeared. Yes, appeared. Turns out, that they were able to control them, making them appear and disappear at will. This was something that even the boys weren't able to do at their current Grade.
Maybe it had something to do with them being born as Neo-Nephilims. The second thing that they discovered was that when the babies absorbed their wings in their bodies, scales would appear on their shoulders. It was similar to the scales on the boys' shoulders.
And the babies were very attached to the boys. Even more so than Katherine and Alexi. Sometimes when they started crying, the only thing that could calm them down was the boys' embrace. This had Katherine and Alexi somewhat worried. Not because they were jealous or anything but because the boys had told them that they would be leaving for the War Academy next year.