how deep does a grave have to be dug for 2 people to go in the same plot?

Answer 1

generally speaking the casket of a person who has been embalmed has to be six feet deep making the top of the casket about four feet under ground. for someone who has not been embalmed the top of the casket must be six feet below groung.

Answer 2

I don't know if you can do this in your state. You would have to check your state statues to find the correct answer, or call a local funeral service to see if they can help. Most graves are side-by-side for this situation.
Good Luck.