Firstly almost all characters from the original books are same but I would add a few more...
So, basically in this book jay has 2 older brothers like they were triplets and jay jay is youngest among them. And percy is also there Jay's step brother.
Jasprit Jare Tripp Mariano
Called as: Jare or Mr. Serious(in joke)
Call jay as: baby girl
Oldest among the triplets always the serious one give death glare to anyone who comes in his way but only softens in front of his siblings.
Usually hides his emotions but in front of jay jay he can not hide any kind of emotions..
Jasprit Kevin Mariano
Called as: Kev or Kevin or prankster(in joke)
Call jay as: princess
The middle one among them always do pranks and keep everyone happy in the worst times also but if anything happens to his siblings instant change and becomes most serious one among them.
Can never handle any joke about his sister.
Percy Rey Collins Mariano
Called as: Percy or Mr. Ugly(in joke)
Call jay as: baby sistah
Step brother of all three of them son of Receey Mariano and Jasper Mariano. Consider the triplets as his own and is currently holding Mariano group until triplets turn 18 and his age is 21. But his mental age is 10 years but if somehow he becomes serious then something is really wrong. And ofcourse self obsessed..
Jasper Jace Mariano
Called as: Jace or troublemaker(in joke)
Call jay as: ate jay
Brother of Percy and step brother of triplets. His age is 14 years but is very intelligent..
About other characters they are same only