Are these red flags or not

My sis is texting this guy and he's our cousin but we (sisters and I) have never really met him in person or ever talked to him because he lives far away from us. We (sisters and I) live in Cali and he lives like in New York or something. First things first, my family don't mind us getting married to our cousins. I don't mind either. This guy also travels the world AND he's in his 20s and my sis is 17 y/o. I don't really like him and so does my other sister.

So, my sister talks to this guy's sister and he heard my sis's voice or something and said that he likes her (or something like that) and wanted her number. He got her number and started texting her but she blocked him. But he got new numbers and always texts her with those number even though she kept on blocking him. He kept on doing this and finally they started texting each other. This goes on for a few months and he always says that he loves her and that he'll marry her. Then lo and behold my sis tells me she fell in love with him.

He came to Cali and oh...my...god...he is close to my (parents) house even though my sis never told him where we live. He took a pic and sent it to my sis and told her he has flowers for her. She refused and said she felt bad for refusing but me being me thought that was creepy.

redflags are:
*He's an adult and my sis is a minor.
*He knows where we live even though we never told him.
*He kept on getting new numbers after my sis kept on blocking him.
*He told my sis that he's gonna make her smoke when they get married. (he really said this) My sis is a good girl and she will never do that. (She said when they get married she'll make him stop)

But he probably is a nice guy because he helps the homeless people and I've talked to him once and he seemed nice.

What do you guys think?