nosy family members

i could never type the full story (stories) to give you a true and accurate over view. but in simplest form: I have in-laws who are nosy. my SIL and BIL they try to copy my husband and i (primarily the wife tries to copy me). it's so annoying. I can't post on social media anymore because they copy us😑 or try to out do us. quite frankly it's annoying and I don't care. but what is more annoying is how we can't really seem to keep our lives to ourselves. because if say our MIL or someone ask about what's going on in our lives it always gets back to the BIL and SIL. at this point I'm sorta venting. but I don't know how to keep ABSOLUTELY EVERYTHING private?! just a ver crazy example: my SIL has been blonde her entire life. I'm a brunette. I was saying how I wanted to go a little darker, get a certain style and get caramel highlights at my next appointnent. And bam 3 days later, that's her hairstyle . mind you I never told her. I was telling another family member who I know for a fact told her.