Thanks again!!!
It's about 6 kids who (for all they know) were created in a lab and were like "lab rats" in it. They were tested on and were treated like animals, injected with bird DNA and they became human-avian hybrids. (They have WINGS OMG) eventually, they escaped together and treated each other like siblings, living together. and Max is the oldest. (she loves one of the boys in the flock, Fang, so it's weird to call them sort of siblings xD)
Then the youngest one, Angel who is 6, is kidnapped and taken back to the lab. All of them are trying to get her back, aaaand you'll have to read it if you want to know more