Well, some knights would live in the castle while others had their own places. You can have Mircea live in the castle with the royal family if you want, or you can have him living with the rest of his family given that they're wealthy enough to lodge multiple people.
He'd have to attend training daily as required for the soldiers of Kagha and have that extra duty to keep the peace in Prira
Being a personal guard to Zak, he'd have to attend any missions or outings that Zak goes on- stuff like that
Well, Zak is going to be a mama bear to Salen & Kris, even though he knows they're capable of handling themself.
Since Kris likes to roughhouse, I can imagine him and Zak getting pretty physical often. Knowing Zak, he'd probably hide out in Kristopher's room just to get the jump on him (and get revenge for being one inch taller than Zak) He'd also save a lot of pent up jackassery for Kris since that's his way of showing his love <3