My sister and I haven't never been very close, but we do speak.
When I have the money and can afford to send birthday/Christmas cards and some money to my nieces and nephews I always do, and this includes my sisters beloved step daughter, who calls my sister mum (my DS has no biological children, and her DSDs biological mum isn't a part of her life anymore).
Last year I had a baby. All of my other siblings sent stuff to congratulate me and my DP. Yet, my sister sends nothing, I would only have wanted a card to say congratulations! Surely it's not hard to send your sister a card to congratulate her on the birth of her child? It really hurt me a lot and made me feel like I'm not important to her (maybe I'm not?), and I can't help feeling quite upset about it from time to time. My DSs first birthday just went by and she didn't even send a text to wish him a happy birthday.
How would you deal with this? Would you say something?