Dick Grayson. Robin. An only child adopted by the billionaire Bruce Wayne. Batman.
But what if Dick wasn't exactly an only child? Yes, he was born an only child, but when a little girl at the age of 3 was left unconscious at Haly's circus, it just so happened to be the Grayson's and their own 3 year old that took that little girl in.
All that she had was a note lying on her. Assumable from her original parents.
It read: "Please take care of my baby girl, her name is Thyme Aconitum and then whatever last name you give her. She isn't safe with me and I can think of no better place for her to be. She isn't like normal humans, but she shouldn't have any powers until later on in her life. Please, I beg of you, take in my baby girl and don't send her to an orphanage. She needs to be on the move at all times, and with the tours you do, this is the best place for her. Thank you very much."
So, the crew took the little one in and she became the fourth Flying Grayson after some training with her brother Dick.
And after a while it was made clear that this sweet little girl was indeed a meta, a meta with the power to control time.
When Mary and John died and Dick and Thyme went to live with the one and only Batman, Thyme was warned to use her powers only in emergency, and that real power was not in that of the supernatural. She understood and joined the Bat Family.