What is a real family?!

Every time I attempt to explain my family tree I get asked, "Okay, so who is your real family?". It baffles my mind, the people I explain in my family tree are in fact my real family. People have started asking my kids the same question, which of the kids are actually siblings and honestly it's one of the most annoying things a blended family can be asked. Our kids realize that not everyone will be understanding of a blended family and ask questions that sometimes annoy them and I have been there too. One of our kids, Hunter, was recently asked if Brooke was his real sister he said"Yes." and then they were confused because they don't have the same last name. I'm not sure when a last name became the defying trait for a family, but apparently it is. Hunter was extremely upset when he was informed Brooke isn't his real sister he and Brooke have been siblings since they were two. In my opinion there's more that makes them a family than blood. They grew up together, they learned to ride bikes together, swim, read, write, and so much more. They've made memories together and realize what makes a family. There's an amazing show I watch called "The Fosters" -I know shocker the person with a transgender kid and a blended family who is pro adoption watches a show like this, not the point though. In the show there is a quote that I often tell to people when they question our family tree and I'm honestly about to get it engraved on something and put it up in our house so the kids can remember it: "DNA doesn't make a family. Love does." I just wish more people thought this way, but please even if you don't share our views on what defines a family don't tell my four year old his sister isn't his sister.