Heather, Hilary, and Hazel
They were orphans, with Pheobe as a caretaker (Pheobe is Chan's twin sister for the fic) there was an orphanage fire, where Pheobe almost died in, saving kids from dying in the fire, they met Chan, soon after, he treated the triplets as his kids before they were adopted by the Hwang family.
Woojin
Woojin was the second one to meet the triplets, and he treated them like princesses, Pheobe will never admit to liking Woojin, ever, but Heather notices and tells Pheobe to "not care what anyone says, and ask Woojin out" Apparently Woojin heard while playing with Heather's sisters, he looked at Pheobe and then asked Pheobe out.
Bang Chan
He first met the triplets when Pheobe showed up at the Bahng Residence's doorstep, crying and rambling on about an orphanage fire. He was confused, but gladly took Pheobe, and the triplets in because he felt the need to keep them safe.
Lee know
He met the triplets during a photo shoot, Chan had brought them (and when they met Lee Know, they were about six, maybe seven years old) Minho quickly felt like he must protect the triplets, so, that is exactly what he did
Changbin
Changbin met the triplets during a meeting with JYP as they were at the JYPE building, just vibing on the main floor
Hyunjin
The triplets were adopted by his family, he met them when his family did. He loved them when he met them.
Han Jisung
He met the triplets, when SKZ debuted as the triplets moved in with SKZ per Hyunjin's request
Felix/Yonbok
Felix first met Heather, then Heather's sisters, he already knew Hyunjin so he found it easy to meet the triplets
Seungmin
Seungmin met the triplets during a vlive where the group was together, but the girls were behind the camera
Jeongin
Jeongin met the girls during school, they were eighth graders at his high school for a tour, as they would be freshmen in a year.