Is it normal to be attracted to younger girls?

I've been attracted to preteen girls for a while now, they have nice skin and nice long legs, etc.. I follow a lot of them on instagram like Taylor Nunez, Kaylyn Slevin,etc... I'm in my teens.

There are two girls that I know in real life that I really like though... There are these two sisters that are the daughters of my parent's friends. Our families are friends and hang out a lot. One is 13, the other 14. The younger one is more outgoing and feisty, while the older one is more quiet and introverted. I was always the cool older boy that they had a crush on. With the younger one it was always a lot more obvious. The younger one was always a lot more flirty, but both were crushing. Our families are friends so we have pool parties and stuff together.

I think they always knew I was attracted to them though; like they would always catch me sneaking glances at them and smirk, sometimes they would whisper things to each other and their friends and giggle, or if I was lucky they would even pose for me; like they knew I was staring and would purposefully bend over and stretch and stuff while wearing short shorts, yoga pants, etc...
Though it seemed like for a while they get over it and stop noticing me and then later start noticing me again. The older one seems to have permanently gotten over her crush on me... :(

I really like them and fantasize about doing stuff with them all the time, problem is if I actually started dating one of them the parents would most likely freak out, as would everyone else... They look amazing though, I would say they're probably half-way through puberty, its honestly so cute watching their little breasts develop and them start to dress more stylish and take care of their hair more. They are pretty good girls with strict parents, but I did see the younger sister getting kinda flirty with a boy once and it really honestly made me pretty mad. I don't like thinking about them growing up too fast, starting to date boys, and do stuff with boys. But like I said parents are pretty strict so probably won't happen anytime soon, but the thought of them with any other boys doing anything; touching,kissing,etc.. really makes me feel jealous/mad.

So... my question is what should I do now? I care about both of them and would never hurt them or take advantage of them or anything like that but I feel like if the feeling is mutual and they have a crush on me, then what should I do?