I'm 26 and dating a girl who's 24.

Basically we've been living together for the past 3 months and things were beginning to get better for us, on a serious note.

About a month and a half ago, she pushed that her 13 year old nephew should live with us, before he was living with her parents (his grandparents).

Really all I wanted out of our relationship was to be alone, freedom to be young and bond. Unfortunately his presence has hindered this for me personally.

To put their relationship into perspective (gf and her nephew), they're constantly arguing about something, there seems to be no affection shown as I set idly by and assess their situation. You know, the kind where hugs/kisses followed by I love you and what not, general feelings shared by an adult and her sibling in a normal scenario. She, for some reason, feels it is her duty to raise the kid when he was perfectly well off - in comparison - to remain living with her parents.

As for myself, I find it very hard to even attempt bonding with the teen, first and foremost I don't want to play the whole father role, especially if he's neither of our kid. Nonetheless, I gave it a shot and feel that it has failed and/or is failing.

I've developed nothing but despise toward the teen, he has no respect for anything of mine and everything in this house that I'm trying to build and keep.

Examples:

He's constantly peeing on the toilet seat, I told him to raise the lid. He still doesn't listen.

I pay for our groceries, lets say for example 10 pack of lil debbie cakes, wake up the next morning craving one only to find he had already eaten the entire box (I'm not exactly rich, food is expensive). Of course, he lies about it saying he only had 1. I refuse to hide food, and this literally happens every time I buy groceries.

I work night shift, he is told to go to bed before 9pm, especially on a school night, he doesn't listen and stays up 3-4 AM in the morning.

He gets told not to get on my gaming console for a set amount of time because he decides to leave 4 bowls of food, drinks and what not in there waiting to tip over and destroy my electronics. Of course, he sneaks in there when we're gone anyways and does it. Not to mention, he constantly screws up my tv's calibration, settings, and whatnot.

He's just making it very, very hard to want him around.

So now, I'm just feeling like in order for her and my relationship to work, he needs to go back to living with her parents.

What are your thoughts on the situation, I'm to the point of telling her, it's either him or me.

Does anyone else have similar experience.