I'm sorry to hear this.
I never wanted kids until the last couple of / few years (DH always has but wants me to be happy - see my other posts if you want more details), and was told in the summer by ob/gyn if we're planning to have kids we should do it in the next couple of years while my I'm in good shape and everything is working, because of complications she sees coming (a hysterectomy is in my future).
I was telling my sister about it, and how DH has always been so supportive. He's always said if I reach a point where I want kids and we can't have them biologically for some reason, we'll simply look into other options. Adoption would certainly be an option and we're both on board if that time comes.
My sister, not the most sensitive person--but has a PhD, is extremely intelligent, and totally gets me--said she didn't have a maternal instinct in her when she had her kids (she was young, barely 22), so if she didn't have biological children she didn't think she could feel an attachment. I told her I definitely could...then, she said... "Well, you were always bringing home stray cats and dogs and making them your pets, so I guess I can see that you'd form a bond." I was so stunned I didn't even know what to say. I've never heard her say anything I thought completely ridiculous, even when I disagree with her, so I basically just sat and waited for her to say she was kidding, or realize what she was was wrong on so many levels. Never did. That was in June and I still haven't forgotten it. I mean, would she not feel a bond to our children if we adopt?
Sometimes the people who love us the most, even the smartest people, say the dumbest or most insensitive things.
Try not to dwell on it. I say this even though six months later I'm still stewing a little. The point is, I guarantee my sister never gave her statement a second thought and yours is probably just as direct as mine (you're probably a peacekeeper between your sister and mother at times, like me). When I told DH what she said, he was as stunned as I was (simply because she has just never said anything that callous or stupid), but he chalked it up to her somewhat ballsy personality. And she is ballsy.
I hope everything works out for you. Congrats on your new home!