Is OTHER wrong in the post ? POST : I don't usually post my problems, but I really don't know what to do. 

So my older brother(29) and I(17) have always had problems. He's always been mean to me and doesn't seem to care about my well being like he does our sister(19). We both live with our mother(54). My mom had gained custody of me 2 years ago. I brought my stuff and I had a Keurig. He really likes coffee, so I let him use it under the condition that he cleans it just enough that it doesn't get disgusting. I rarely use and when I do I use it for hot water, which is another reason why I'm not sure if I'm being the asshole or not. He had been using it for awhile and I decided to use it so I could have some tea. I thought that since I was using it, I should wipe it down a little. This is what I call his "first offence". The tray was so sticky that the top wouldn't come off and when it did come off I discovered that there was mold growing inside of it. I was disgusted and told him to clean it or he would lose the right to use the Keurig. He didn't, until three days later when my mom yelled at him for it. He started buying water filters for it after that, so I let him continue using it. 
The "second offense" came a little later. This isn't as bad, but after the mold incident I was less forgiving. He wouldn't clean out the ground that would collect in the top. So I asked him that if he was going to use it for coffee, if he could clean out the grounds that got left there. He didn't, until my sister got involved.
 The "third offense" is actually four of the same occurrences. When he would switch out the filters he would always misplace one, or he just wouldn't see it sitting there on the self. If he didn't see it he would yell at mom and me for moving his things. After the fourth time of this I took my Keurig, cleaned it out and packed it away for until I move, so that he can't use it. 
It belongs to me, so I feel like it shouldn't be a big deal if I take it away, but why do I feel like the asshole. Am I the asshole for taking it away?