2 yr old dog has separation anxiety away from his brother?

i adopted a 2 yr old yorkie/terrier mix from the SPCA yesterday afternoon.. he had a brother that he stayed with in the kennel but i could only get one of them, ever since i took him home he wont eat. he doesnt cry and he seems like hes pretty happy here but its scaring me that he hasnt eaten since we've brought him here, ive tried 2 different kinds of dry food and wet food. the only thing i could get him to eat was a piece of turkey, and he wont eat anymore of it, just a tiny piece. any suggestions or anything? and no i cant get another dog