Question
my father-in-law has tomatoes that or rotten inside at the seed pods. What is the reason for this and how can he fix it?

Answer
If I understand correctly, the seeds are rotting as they are germinating. If this is the case you need to buy need seed that have been treated for fungus and virus. These seeds are coated.

If tomatoes are rotting this most likely is caused by a fungus. You will need to spray with a good fungicide.

Please let me know how the situation develops.

Best wishes.

Don Battles