Is this unfair, read description

In my house all of my siblings and I are equal with most things like what movie we can all watch. My siblings are older than me by 6 months and 2 years (half siblings). I rotate between houses. I also follow them on IG. In the past few years and recently my dad has said I can’t watch a movie because it’s rated R even though its actually PG-13. I woke up and looked on IG stories to find that they are watching the movie I have been told I can’t watch. I’ve proved to him that it’s not rated R before ski it’s not that he just found out. My dad knows my wall between what I personally feel I can and can’t watch. All while my dad has told me no to watching it. Just wondering your opinions on my situation.