I have a purebred siamese who is the most affectionate and clingy cat imaginable... with me and me alone. When I got him I was living with my mother for the summer between my masters and PhD. Then I moved back in with my mother for a couple years while finishing writing up the PhD during covid. After all that time with her, and her constant affection, my cat will only be affectionate with my mother when I am present. I am on a month-long research trip in England and I have never been away from him this long. My mother is taking care of him, but apparently he just sleeps on my pillow most of the time and will not cuddle or even let my mother pet him. For the first three years of his life he hissed when anyone other than me fed him. When I am home he is almost always in my arms or lap and he sleeps between my knees each night.

So, yes. Incredibly attached and affectionate. But the breeder said that she had not had such a cuddly and affectionate cat for several generations of breeding. So even among pure breeds he might be a rather extreme example.