Annoying questions re non-sibling triplets

I was hoping for some advice on how to respond to questions about my kids. Our children are African whereas we are not, so it's obvious that they are adopted. We also happen to have three of the same age. They have different birth families (with birth dates close to each other) though they have been together since soon after birth. We usually refer to them as "triplets". One of the first things almost all people want to know when they meet us is whether our triplets are biological siblings or not. People mostly ask it in front of the children. People approach it in a lot of different ways, sometimes asking if they are "real triplets?", "are they from the same family?" or other more subtle ways. I'm really not comfortable with the frequency of these questions because I feel it's not helping the kids' sense of family unity for me to have to regularly tell people they are not biological siblings. But if I respond in a way that might leave the person with the impression they are biological siblings (like "yes, they are real triplets", which to me they are) then it leads to further comments, questions and misunderstandings. (People are just naturally curious about multiple births and want to ask more). Plus, I don't want the kids to get the impression I, or they, should think there is anything shameful about them not being biological siblings. Does anyone have any advice about tactful responses to these questions? Thanks.