Junior Comparative Etymology

My work with children has always been full of all sorts of interesting anecdotes, but often it even delves into my work just a little bit (as can be seen here, here, and here). One great example just happened a few hours ago. The notorious Blake (with his own posts here, and here) asked me to say something in Ukrainian. This happens to be a pet peeve of mine, and one of many people I know who speak Ukrainian, or just about any language really, but it's actually quite duplicitous in that I love the opportunity to show off my stuff, and love it when people take an interest in my language. As such, I asked him what he would like me to say. He said "sun," and after I clarified that he did not mean "son," I told him the word was сонце [sɔnʦɛ], and he gave the following response:

Sontse! It's like sol in Spanish and Italian, and sun in English! Why do they all start with s?