The only way you could possibly be violating the commandment to honor your parents is if the relative who are asking you are your parents. You are under no obligation to extend the same honor to your Aunt Mabel or your Cousin Patrick or your brother’s wife or anyone else. The question then rests on some conditions.
First of all, are you an adult? If you are, and you don’t feel comfortable sharing this information with your parents, then you can find a polite way to tell them that you don’t want to share. If they are genuinely concerned about your well-being, then you might make them feel better by telling them that you ARE communicating with someone who can help in the situation. (doctor, police, lawyer, counselor, or whoever)
If you are a minor, then you should probably give you parents the information they want, as they are probably trying to help you. The only exceptions I would make to that recommendation would be if you have already told them the information and they are simply making you relive it because of their own curiosity, or if you think they would use the information to justify their or someone else’s abusive behavior toward you. It’s hard to say what to do in that situation, since we don’t know what the circumstances are. I do encourage you to speak to someone who can help you.