How do you find out if you're a good singer?

I LOVE to sing! Music is a big part of my life and I THINK I'm a pretty good singer. I'm even planning on trying out for the X-Factor when I'm 17-20(I'm 14 now). I do think I sound kinda weird on a recording, but that's normal. Everyone thinks their voice sounds weird on a recording because your voice sounds a little different in your head then in real life. Anyways, sometimes at home when my parents aren't there I watch karaoke videos on YouTube and start singing. My little 11 year old brother tells me to stop and says I'm horrible. This really brings me down a lot. I don't know if its because I'm distracting him from playing video games, if he doesn't like the type of music I'm singing, or if I'm really terrible. I can't ask my friends because whether I'm Good or not they're still going to be nice and say I'm Wonderful. Same with Family. Please Help. I can't imagine doing anything else but singing or acting. Thanks. :)