What do you mean mostly? I thought it is their whole youth team that took places of their first team. Actually after reading your post twice I guess you wanted to say the same but word "mostly" added some confusion for me 
Technically you're correct they're all from the youth team but gpk and Kingslayer only started playing with the other three core players officially after they were all moved to the main team. I should've used "half" instead of "mostly" my bad on that part. 
RNG - PSG - O3.5 maps + Vitality moneyline @2.48
No sweat on the over 
I also took the same bet since I still remember that RNG loss during the rumble stage.