Question about survivor's benefits for a minor child

Sorry if this is a stupid question but my emotions are currently in overdrive. BFF's 40 year old son is terminal and on hospice. Divorced with a nine year old son. He has worked for the past 12 years as a teacher but has some SS covered work before he got on with the district. Does he need the full 40 credits for benefits for his son when he passes or is the 40 credits just for retirement?