Thirteen years ago, in a secluded lab, scientists experimented with humans illegally.
They would attempt to make people geniuses at birth, superstrong, and, among others, hybrids.
Out of this immoral deed came three human-avian hybrids, Project Tenshi.
Project Tenshi was an experimental procedure that tried to infuse avian(bird) DNA into Alices. Only the three survived.
Through the avian DNA, they inherited things like raptor vision, an increased heartbeat, more airsacks, and assorted powers.
Oh, and I almost forgot. They also have wings.