you've just started your working career and unfortunately you'll come across many of these people throughout your working life.
these type of people have their own problems whether it be at work or at home and you will learn to deal with them in an adult/mature way, and not let them influence your decisions, etc
they may also see themselves as being a wee bit over the hill and not going anywhere now, and may resent that you are young and starting out in your career.
best of luck in your career ( coming from someone who is a wee bit over the hill, but happy and content with it !! )
Iain