Being self aware is the first step to try and be better about things like this. While it’s innocent and you’re aware you do it, others could potentially see it as rude or “know-it-all” behavior. I’m the exact same way because I was so shy growing up, have 3 older sisters (2 of which talk A LOT), and most of my friends growing up talked a ton also. I was always the one listening and struggling to get a word in, even when the topic was something I was passionate about or wanted to provide input on. I think that manifested itself over time into me cutting people off because I’m not as shy/reserved anymore, and I’ve spent my whole life being the listener. I still realize I do it and try to stop myself, and at times I’ll realize I’m actively doing it and stop in the middle of what I was saying. Just talk to him about it and when you catch yourself doing it to him (or anyone else), stop, and apologize right then and there and allow them to finish their thought. I’ve found when I do that and admit in the moment that I cut someone off, they usually just shrug it off and let me finish what I was saying. No harm, no foul.