Is this normal?

Wednesday will be the two year anniversary of my sister in law's death. (my husband's sister). She and I were very close and I miss her a lot. Since the anniversary of her death is in a few days my husband and his family shut down completely. He called me from work havign an anxiety attack this morning and was unable to function. I have never lost a sibling and I cannot imagine the pain that comes with it but is it normal to wallow in the sadness and not be able to function two years later? As bad as it sounds his family enters this somber state a few days prior to the anniversary and almost plan to be miserable and depressed. They make statements like, "I am sorry if I will be snappy or seem rude but the anniversary is coming up and it is hard to believe it has been almost two years." What can I do to help him get through this time without feeling guilty for not being so depressed?