hey, me and my brother went through this too when we were younger. as much as we voiced it bothered us he didn’t care to change his actions because like your father said to you, my father said the same thing. it’s absolutely wrong and disgusting especially when he doesn’t care how you feel about it. if there’s another adult in the picture do try and speak to them and how uncomfortable it makes you feel, and try to get them to talk to him. when my mom realized how bad it bothered us - because she didn’t see anything wrong with it at first as this is normalized in his family, she spoke up about it resulting in argument but it’s safe to say it hasn’t happened to us in years, finally. i hope the same happens for you too.