His behavior is inappropriate and I would be cautious of him. He's disgusting to flirt with a relative especially a close relative like a cousin. I’m not sure how old you are but don’t allow him to prolong this. I dealt with a non biological cousin who liked me and it put me in a awkward situation to tell my family. I of course rarely had to see him so I didn’t have to take action urgently. I told my big sister who made sure he would never come near me but I didn’t want to tell my mom because that was her nephew ( not biologically but we were in the same family so we considered each other relatives). Especially if he is older than you, he is probably a predator. How I handled my weirdo of a cousin was that I told him he couldn’t message me on social media anymore. I bluntly told him he was gross and what he was doing was wrong. I told someone. If you have to see him frequently make sure to please tell someone, particularly your parents. Please do not be alone with him, keep you distance. Creepy people are everywhere, especially in families. Stay safe and take precaution.