This happened about a decade ago. It was my sister's birthday while I was in China. By that evening, she said the day would be perfect if she could hear from her son. To make her happy, I sent a gentle reminder to her son.
The young man told me, “I abhor being told to do things like this. If I send her a birthday wish, it's because I feel like doing so, not because someone told me that I should." My face burned when I heard the annoyance in his voice.
On the one hand, he was right in many ways. Nobody enjoyed being told to do this or that. He was right when he preferred to act out of his own heart rather than from external prompts, and when he emphasized genuinity rather than obligations in relationship between adult children and their parents.
On the other hand, had I done something wrong when I didn't want to see my sister being disappointed on her birthday, when her son meant so much to her?
Understandably young people are busy with their work and other social life. It's okay if they are too busy to remember parents' birthday. For sometime I could see his point but still believed that I had done the right thing by sending a reminder.
Effective communication is the key in all relationships. Perhaps the key is missing here. To avoid disappointment, perhaps my sister should be upfront with her expectations unequivocally instead of waiting and expecting silently, like telling her son, "I'd like to hear from you on my birthday." I'm sure her son won't forget it. In fact, this is how I communicated to my children many years ago.
沟通是关键 (gōu tōng shì guān jiàn), communication is the key. Ultimately things won't go too far off with open and honest communication, especially between parents and their adult children.