The arrival of a new baby sibling can be a little disconcerting for a toddler. One way to make it easier is to go get a baby gift that the older child can give to his little baby brother. Let him help in picking it out at the store so he will really feel like it is from him. This can help the toddler transition into his role as a big brother and he can feel important instead of like he has been replaced.
Encourage your toddler to contribute with every day baby care also and he will feel included. This way instead of resenting the little one who has everyone's attention, he will be part of the action and be proud of himself for being such a great big brother.