My son's g/f 23 yr old lost her mother to a long fight with cancer. This poor gal barely has any living relatives, her father died when she was very little. What my husband, son and I have found out is that the loss of a loved one is devastating for the only surviving person. She has been grieving since last Fall. It just takes time for healing to come. You can lavish all your love on your father...but it will just take time especially since they have been together for such a long time. I pray for God's healing touch upon your father.