Jess Mariano is Luke's troubled nephew that comes to live with him during season two of Gilmore Girls.  He's played by Milo Ventimigilia and is definitely a love interest and part of a love triangle between Rory and Dean.

Jess Mariano Quotes

Lorelai tries to get Jess to understand that Luke is trying to help him
Jess: What are you sleeping with him or something?
Lorelai: Excuse me?
Jess: I don't know. The whole starry eyed 'you're so much better off, just give it a chance' speech. You're either really nave, or you're getting some.

Jess: Wanna play some poker? Five bucks a hand.
Luke: No.
Jess: Ten? I can't go any higher than ten.
Luke: Jess-
Jess: Okay, fifteen.
Luke: I don't want to play poker.
Jess: You sure?
Luke: Yeah.
Jess: Okie dokie.

Gilmore Girls Quotes

Emily: What are you doing?
Lorelai: I'm taking out the avocado.
Emily: Since when don't you like avocado?
Lorelai: Since I said "Gross, what is this?" and you said "Avocado".
....(later)...
Emily: What's wrong with the tomato?
Lorelai: It was fraternizing with the enemy.

Luke: Me? Raising a kid? I don't even like kids. They're always sticky like they've got jam on their hands. Even if there's no jam in the house, somehow, they've always got jam on their hands! I'm not the right guy to deal with that. I have no patience for jam hands!
Lorelai: First of all, Jess is 17 so I think he's probably pass the jam hands stage by now. Second of all, you can do this. If you want to you are totally capable.