Personally, I'd blink at them, raise an eyebrow, and say with absolute incredulity, "ExCUSE me?!"

...Could go into "Didn't your parents tell you the customary response to happy news?", which could get funny, but eh. Personally, I meet the lack of common courtesy with as much sarcasm and my own mix of rudeness as possible.

By the way, have fun raising those two! Hopefully they're not like me and my sister, we fought like cats and dogs growing up, although we were about 26 months apart.

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