M.J.
My kids are different ages: my daughter is almost 3 and my son is only a little over 2 months, but I'm running into a similar problem. Both want me; dad's not a substitute :o) What I've done is I started taking my daughter out just for "Mommy-Caitlyn time" - even if it's just errands. Then, every once in awhile, I get her a little toy or something while we're out, and I explain to her that it's because she's such a great big sister and because she's so understanding about how her baby brother needs me sometimes. It seems to be working pretty well - of course, not ALL the time, but I can remind her here and there, and she'll go along with it. Anyways, just a thought! Good luck!