Awww hun some people just don't know how to be happy about anything do they. Having the new baby around is so special for everyone! A few things that I have loved seeing...
The way they just adore each other more and more each day and the way Iz will say "Mummy, James is my best fwend today"...
The way she just wanted to cover him in hugs and kisses all day long when he was a baby.
When Iz would breastfeed her dolls because that is all she saw all day every day!
The way they both fit perfectly under each arm for story time and you can give them both big squishy huggles.
The way they are growing up together as such wonderful, beautiful friends and every day really is just priceless.

We never had any jealousy issues here at all, so it all just depends I guess! Good luck hun, it really is just awesome!