I just realized I never explained how Felix got his powers.
So here it is: Pretty much vampires have a slight chance (like 1/1,000,000) chance of being born or developing powers. There is a wide variety of powers, which I'm not gonna go into, but Felix developed the ability to read minds.
Hopefully this explains a little bit more.
Also about how they age. So, whenever they become mature they stop ageing. By mature I mean can actually be considered an adult, or have an adult mentality.
This is hard to explain, sorry. If you need me to try my best at explaining it more, let me know.