I'm so sorry you are dealing with this. My sister has 10. I ALWAYS get "is she crazy?" I'm so sad about this comment, I often don't even mention how many kids she has. I have 1boy, my oldest sister has 1girl and 2 step-sons, my other 2 siblings are not going to have any kids. I have even heard people tell me, "you're family is like rabbits" and such things. I don't think they know anything about my family!!!! It's so frustrating. My youngest sister, in fact, is vegan and has on a profile on-line that her goal in life is to leave very little impact on the planet. Yet, she and all the rest of us are called rabbits.
Here's a good one. My sister who has the 10 children said that a woman once told her "You should put some condoms in your shopping cart." (She probably had 4 kids at the time.)
My niece was just learning about pregnancy and said "Is she having a baby or is she just fat?" hahaha This is the one and only time I've ever heard of anything mean coming our of this girl's mouth. She was 2 maybe or 3 - very young. She's always been super witty though and SMART! haha I wonder now if she knew what she was saying.
Then, of course, the lady said my sister's kids were so rude, but inside my sister was loving it.
I could go on forever, but one last thing. Just try to be lighthearted about it. Those people are rude, busy bodies. My sister and I laughed before about making t-shirts for her family that say, "no twins", "yes, we have a tv", "we drive a van", etc. So, they could answer all the questions before they were asked.