I keep staring at my sisters chest. Do i have mental health issues?

dating underage girls is wrong. But wanting what you can't have is actually more normal than what the people on here are going to admit. I highly advice having sex with your sister. I don't think anyone here will admit they've once noticed their family memebers once or twice in some sort of sexual tension, but as long as you don't dwell or act on it. I mean, its still weird, but deffinetly not uncommon.