In general, I think the biggest beef is that a lot of these comments come from complete strangers or casual acquaintences. It's like being ask to tell your labor and delivery story to people whom you don't know.
Real brothers and sisters...yes I know people want to know if they are biologically related. Sometimes, it just really isn't anyone's business and sometimes, it's about the fact that the word "real" makes it seem like adopted siblings aren't really siblings.
So lucky...this one does make me cringe. I know it's a compliment but 1. we are not saints and 2. my children are not lucky; there is nothing lucky about losing your first family, losing your second family (orphanage or foster family) and having your early life look extremely different than just about everything else's
Hair...petting people is never acceptable, especially if you don't know them. Once is not so bad but my children get petted a lot and honestly, it gets a little annoying to them.
Cost...just plain rude when done in front of my children unless you are seriously interested in pursuing an adoption and are trying to gather information. If so, clarify this and ask when a good time to talk is. Mind you, I am not opposed to discussing the financial end of adoption; I just don't want my kids feeling like a commodity due to the way someone words their questions.
Where are their birth parents?...most people are asking out of curiousity not because they have a really important reason for asking. If you are a stranger or casual acquaintence, I'm not sure it's your business. This question puts me in an awkward position because I don't want my children to feel ashamed of their story but I also don't want them to feel like they have to share their private story with everyone who asks.