Is middle child syndrome and actual thing? Opinions please?

So I’m a middle child, and I always noticed that I was over looked/didn’t get treated the same. I have two sisters, oldest one who did everything under the sun and didn’t really get a punishment. Youngest one does whatever she likes without any questions being asked. Where as I was always the one to get grounded over nothing, such as not dusting the tv unit once after I had cleaned the whole house top to bottom. My sisters would always get asked if they could do something and when they said no to my parents then they would just come and ask me and then get pissed if I said no, and don’t get me started on birthday parties because I honestly don’t know what it’s like to have one but my sisters have told me they are fun. Obviously there’s way more to this story but I don’t think my thumbs could take the abuse from how much I have to say 🤣

I would like to know what your views are on it? Are you a middle child and got treated differently? Or is it just me?