I have 5, and have several friends with 5 and more. My response to every single comment, no matter what, is this:
“I have come to believe that the greatest gift I can give my children is their siblings (a quote from Pope John Paul the Great).”
When they are adults, they won’t remember how much money I spent on my brick sidewalk, my car, or if my bedroom set was solid cherry or came from a consignment store. They’ll remember laughter and tears, fights and handshakes, chores and hard work, but most of all, they’ll have character and will know they were loved. I once had a woman look at me with such disgust, I actually thought she was about to spit on me. I stared her down and never broke eye contact, and kept the smile going as I lifted my toddler up and kissed his head, and then I winked. She looked like she wanted to throw up! But I made sure that image was left in her mind.