Q:

Is my 2 year old son jealous of his kid brother? 

my toddler son is two years old, one month ago I and my wife were blessed with the birth of our 2nd boy. 
My old son seems to understand the situation and welcomed his kid bro at first.  Recently, however, my wife raised concerns that he might be a little jealous of the little one.  
What she observed were:

he shows reluctance to visit his mother if my wife is with his kid bother;
for once he made some unfriendly moves toward his brother, like pinching his legs - not to the extend of real harm, though. 
he was already little spoiled and now becoming more demanding for attentions, for example, he insists on more hugging and carrying in arms, which I urge my wife and relatives not to do, as he became very heavy now and I am afraid he would become less independent. 

I thought my wife was over worried, nevertheless, to be fair, is her concern legitimate?  And what should we do if it proves so? 

A:

Yes, your son is jealous, that is almost inevitable.  
Yes, your wife's concern is legitimate, though the situation sounds fairly normal, not alarming in any way.  It can however get worse if not managed. 
What you should do is give your son a distinct role and position as older brother.  Be explicit about the 'privileges' he is getting that his brother is not: Different toys, a bigger bed, being allowed to do stuff by himself or help with things, etc.  Basically, present all the things you were going to give him anyway (as part of his development) as belonging to that special status of bigger brother.  
The intent is to make him feel his place in the family is secure.  Currently he measures that by quantity of attention spent on him vs his baby brother and he's losing badly.  By explicitly giving him a different place and measuring it in ways that don't depend on time spent, you can hopefully alleviate some of his jealousy.  
That doesn't mean it's a replacement for spending time with your undivided attention on your son!  Quality time interacting with your son is by far the best way to make him feel secure and happy, but if you can't always make time, this is a good backup.