I'm so sorry. Families should stick together in times like this. Does he have any other siblings or parents that you may be able to reach out to? Do you have your own support system? This can't be an easy time for you. Just having to go to work and think about this must be exhausting and overwhelming. How old are your children? Call your family, friends, whoever you can. You need help and support too. Cancer affects the whole family. I would call your family physician. They can help you with the depression. Give you something to help you deal with all of this.
Please take care of yourself.