Dear Fertile Sister In Law,
Thank you for the wonderful mass email you've included me on to detail your new baby's progress. I feel so freaking delighted that you have produced a perfect specimen of a person. I am also so happy that you haven't let my infertility be a downer on your happiness and mention it or make any allowances for it. I would have hated for you to go to the trouble of writing a seperate, sensitive email just for me. That would simply be uncalled for.
It's so wonderful that you'll never have to feel the absolute terror at the thought of never having an opportunity to "naturally" have a baby. That you might never "unnaturally" have a baby. That babies may not figure in your life at all. It's also just grand that you don't realise that your email may have a devestating effect on my sanity. After all, I am just delighted with your baby news. Thanks for not-asking how I'm doing. It really touched me.
The Barren One (aka as your Stranger in Law)