Is it possible that a 14 year old is acting out since his brother (who he is very close to) left for college?

This 14 year old is very high spirited and high energy, but since his brother left for college he has been acting out negatively. He's not interested in school, his temper is ready to go at any minute. His older brother is the opposite: Quiet, mild mannered and a role model. Is it possible that the 14 year old is suffering from some kind of separation anxiety? Please, only individuals with knowledge or experience reply. Thanks in advance!