I really resent my parents for labelling us as children

It does sound like they really tried their best with them. It’s not like they were giving them unpleasant labels, if the op and her sisters were ‘the fat on, the lazy one and the thick one’ then I’d agree. They really tried to identify their strengths and did everything in their power to help them excel. I’d have loved my parents to have called me anything like clever or pretty or sporty.

I think therapy is a good idea.

But you know what? Parenting is really difficult. There's no training, no manual, there wasn't even Mumsnet when you were little. It sounds to me like your parents made mistakes, but were trying their best.

Think about how you'll feel in twenty years time when your DS thinks about you in the same way you think about your parents. Because you will make parenting mistakes too and he will hold them against you...and so the cycle will continue.

But yes, therapy. It'll help you get to grips with the mistakes they made and hopefully come to terms with them, work through them and move on.

By stereotyping children adults have a great deal to answer for.

My younger sister was the favorite. She was also a very pretty child with a mop of curly white blonde hair. I was plain and gawky with mousy hair. I was also a lot more academic than her. That created problems at both at home and in school. In school I was the teacher's pet and top of the class. At home my father hated to see me with a book. When I was revising for GCE I was told to "put that away and help your mother in the kitchen." When I told my father I was revising for my exams I got a beating for answering back. He was not interested in my getting on. That would have been disrespectful to my parents to want anything better. Many working class parents had that attitude in the 1950s.

I alsolutely hated sport and was useless at it. My sister was very sporty and learned to swim at an early age. She was average in the academic sense. All through her school career she was compared unfavourably with me. At home I was compared unfavourably with her. The result was that we were never close even after both parents died. Even now there is a shadow between us.

Get over it OP, either consciously or with therapy. They did what they thought was investing in and encouraging your strengths, just as you’ll hope to do for your children. Parents are humans too and nobody gets everything right.

You need to read the book 'The Favourite'

Oh dear. It is very likely that all this pigeon-holing was, as you hint, intended to help you each develop your own personality. But of course it didn't, it just made things difficult that might have been easy. On the plus side, they obviously put lots of money and energy into making sure you had opportunities.
It is possible to absolutely groan at the damage done us by our parents without in turn labelling them as manipulative or controlling or mean. They would probably be horrified if they realised how hard some of their parenting made your lives. Could you forgive them and move on?

Definitely chat to a therapist about it all. Your parents sound manipulative at best. I doubt they will ever admit any wrongdoing or try to work through any of it, a professional and unbiased opinion would be a good idea.

Therapy's a great idea. This stereotyping - and the adult issues flowing from it - is a really common experience, sadly. As you're already thinking about it, you could already be in the right frame of mind to begin exploring the topic with your sisters if you get together over Christmas. How do you feel about the thought of opening things up with them? They've probably had a few thoughts of their own, it's amazing how validating it can be to discuss the 'unsayable' with the people who went through it alongside you.

Tiny tale from my own, longer story: I was telling some family friends a 'funny' episode from my days as a fat schoolgirl. My brother gave me a look and quietly said "You weren't fat. You were an absolutely normal-sized kid." I was 58.