Are Primary keys needed in child tables?

Are Primary keys needed in child tables?

How important is having a defined primary key in child tables?

Here is my dilemma; I have 35 groups running around come desert country. I
having them send updates to a central database with something like XML files
(I haven’t exactly figured out how yet).

The primary table won’t have any conflicts, but I am contimpated the need to
have primary keys in the child tables.

Could you guys let me know what you think and if it’s worth combining a
group ID with an Auto number in the forms (or if there is some way to have
the Jet do it maybe by default?)