My birds just died,someone help me please?

hello,I have had two pet birds since August 2010. Later in September, they had had four baby birds. These six birds all together had been living peacefully. However yesterday two of my birds had died. I know that one of them was an adult bird and the other one was a child bird. I have been very sad because of this. I have noticed that the four remanding birds are sad as well. They have not been moving around in their cage nor have they been singing like they usually do. It seems like a sad moment for the birdies. My mother sad that she found one of the birds dead in the cage and that the other one was having difficulty breathing and that when my mother tried to help him,he/she had vomited all over her hand and that is when he also passed away. It is weird because they have always seemed fine. I really miss them and I know that so do the other birds. How long will the birds remember and will they get over it? Or will they continue to be sad for a while? Because I really don't want my birdies to be sad. Thank you all,and any additional information would be appreciate.