yes..sure...as per rules,its not allowed but in majorly all mumbai CR trains, TTE comes to check tickets only after kalyan. In koyna also,tte will come after KYN to check tickets.
12106 will surely arrive KYN before 0900hr. I think it will reach by 0840hr,so ur brother can easily get 1hr buffer time at KYN as koyna doesnt arrives KYN before 0940-0945 hr.