How long have you hunted this property?? If it's a pretty good amount of seasons I would reflect back to those as proof that if you were going to sue, that you wouldn't have waited this much time to do so. I would also sit the concerned sibling down one on one and just have an open conversation about both points of view if thats a possibility. I guess it all depends on how near and dear this particular place is in your heart. Either way good luck, hope it turns out for the best.