I agree, I don't see this question as this huge privacy foie-pas that other people seem to. I mean, most couples DO have children... most couples WANT children... most couples have children somewhere in their marriage, so asking your newly married relatives "So, thinking of kids?" is about as commonplace an assumption as "So, thinking of getting new cabinets?" Yes, yes, children are a lot more expensive than cabinets, but I think turning this simple question into an OMG YR INVADIN MAI SPACE!! is a bit on the overreactive side.

Additionally, these are relatives. The older I get, the more convinced I am relatives exist to teach us empathy for even the stupidest life forms, and their sole mission in life is to embarrass me. Frankly, I'd much rather be asked as a newly wed when I'm planning on having children then "You know how to use condoms, right? I've got some here in my purse if you need them."