There's something to be said for giving attention where it is most needed (not necessarily most wanted). My lovely kind parents were at pains to treat their two children equally. But my sibling needed a great deal more attention than I did, and I think his later problems in life were largely to do with an insecurity which was incomprehensible to me but very real to him. I think it can be hard to fathom either way. But really hard for parents too. We all just do the best we can.