My brother's best friend's little brother

Tina's brother JR and his friend (Mack) grew up together, Mack mention that he has a little brother as the same age as Tina, he was raised with his grandparents andhe would be visiting Mack's family for one year, Tina wants to meet him but things got mixed up later on BOOM 💥

What will happen? would they be close friends? read if u wanna find out