I will never know why parent's do this. Favouring one child (and grandchildren) over another, esp when the child that tries the hardest is often the one overlooked. I've seen it time and time again :-(

It happened to me too - I was the only kid who travelled every 6 weeks to see my parents 300 miles away, phoned them every day, sent them gifts & things they wanted in the post etc, while my brothers who did nothing, don't even like my parents and the sun shone out of their backsides.

I no longer talk to my parents, after a huge row with my dad, who told me all sorts of horrible things, swore and called me very nasty names. They refused to talk about it, despite me asking so after few years I came to the decision to walk away for my peace of mind. Now while I don't recommend you be as extreme as I, I do think that perhaps taking a step back, try become less involved and protect yourself from emotional hurt. I doubt very much that you can ever compete with your sister and I suspect its an unfair race already won, due to the irrational behaviour of your Mom.

Try and fill your life with your own things, your kids and partner. Do fun things on your own, perhaps visit less, and rely on your Mom less. It may just let you let go of the anger and resentment...

I do wish you well. Hugs