Dear nieces and nephews- I remembered your birthdays and gave you presents every year until you were 18. I give you a christmas present every year. I took all of you (individually) on a special outing or trip when you were 10. I've never asked anything of any of you, because I didn't do these things expecting anything--but not one of you invites me anywhere or to do anything unless it involves me giving a present. Is it to much to ask that one of you might invite me out for a lousy cup of coffee or something?
I heard the same thing from my 'forgotten aunt' (actually it was my Grandmother) Here's what I would have said to her if I knew she wouldn't have flipped out. You might want to think about what I say from the neice/nephews perspective
(I AM NOT SAYING THIS APPLIES TO YOU, BUT CONSIDER THAT THERE MIGHT BE A REASON THEY NEVER CALL YOU)
Dear Grandma,
I'm a college student now, and my life is extremely busy. It would be nice to hang out with you and have coffee, but if you are going to bring up that trip to the zoo when I was 10 every single time you see me, you should realize that I'm tired of hearing about how grateful I should be about it. I'm sorry that I threw up at lunch that day and ruined it for you.
Maybe you should consider that every time I see you, you spend half the time we are together comparing me to my cousin, who you seem to think is perfect. Honestly, I'm tired of hearing how perfect she is and how I should try to be more like her. I'm not her. Sorry you are so disappointed in me, but you make me feel about an inch tall and not worthy, so it's not fun to hang out with you.
When I do call you and visit, you then complain that the restaurant where we have lunch is far inferior to how it used to be 'back in the day' and you steal all the packets of sugar and stuff your rolls in your purse, and frankly, it embarasses me.
Then when I have to take you home so I can go to my afternoon class, you complain about how lonely you are and that I never stay enough. I'm sorry that I can't spend the whole day, but you should realize that I am making an effort. And please, don't call my Mom afterwards and tell her that my hair is appalling and I should have dressed up more.
Love, your granddaughter who feels like spending time with you is a huge chore.
Seriously, my Granmother used to make me feel like crap everytime I visted her. Is it possible that you are doing the same and don't realize it?
OF course it is also entirely possible that all your neices and nephews were raised with poor manners. And if that is the case, I'm sorry

maybe it would be better to find some other neighbor children/young adults to get close to.