Little sisters boyfriend...😒

Okay, so I am almost 20 and one of my younger sisters is almost 18. About 6 months ago she started officially dating this guy. He is in the Navy and is 21, almost 22. They met through Instagram and started talking as friends about 2-3 years ago. He is from the same city that our family is. Coincidentally....I was acquaintances with him for a very short time before he even knew her...and let's just say I know some things that she does not.

I hate this kids guts. I know that prior to dating my sister, he was pretty good at being flirtatious and getting what he wanted with women. He posts smart ass responses to me if I tweet something and then tells my sister he was "just joking around" but after awhile it gets old. When he met my dad first the first time, he walked over to shake his hand and had his hand in my sisters back pocket! Where I come from...that is a total NO when introducing yourself to your girlfriends father. But then he proceeds to give a wimpy ass handshake...I mean, my cat could have shook my hand firmer than he did. He made some smart ass remark to my dad about his balding hair and claimed it was an "ice breaker" to a conversation. After 2 months of dating my sister, he was overseas and already posting pictures of houses to my sister on facebook saying how he wants these kinds with her and how insanely in love he is with her......2 months people 😑

I am wondering if I am just being petty or if you ladies wouldn't like him either? It is my little sister after all. My parents are telling me to be nice and accept him but I really just have this gut feeling that he is wrong for her. I know she might have to figure that out on her own but I really can't stand him. Luckily he is only around rarely. My bf and I are going to a family dinner with them and my parents and and praying I don't leap across the table to strangle him 😤