Am I right to be angry?

So my brother and his wife have just announced (at my baby shower) they are trying to have another baby normally I'd be thrilled for them. But since having my nephew 4 years ago they were dead set on not having anymore children. My brothers wife is a bit of a jealous person and I feel like she wants to have another baby to take some of my baby's spotlight away. Am I over reacting? Or am I right be be a little mad?