What causes someone to have no empathy?

My husband has no empathy. My BIL has weeks left to live from cancer and I went to stay with him for a few hours so sis could run errands. When I got home, husband asked nothing and wanted to know if I wanted to go out to eat or dancing! I am emotionally drained! It isn't just my family issues, everyone gets along well. His own brother caused a bad wreck (blacked out/diabetes) 2 dead. He called my husband,crying, suicidal. Before hanging up husband said to him "let me know if you need anything." The end. Never even a follow up call to see how he was doing! He told me if his bro wanted him to go visit, he would go. He is generous, will give if you ask, but never volunteers. Not once has he asked how my sister is holding up. No interest in other's issues. Are people born this way? How can someone not feel bad for someone else? Can something cause a person to not give a care or act as if they don't? Is this a psychological disorder? This just floors me!