New kitten need help asap?

i just got a 6 week old kitten im keeping him for 3 days and then hes goin to my boyfriends house where he has an almost 10 week old kitten n he is alot bigger the kitten im keeping crys everytime i leave the room and he hardly eats i got him yesterday n i want to know if he'll stop crying when hes with the other kitten and do you think theyll get along and how can i get him to stop crying everytime i leave the room its so sad