Repeating group header names

I am trying to group data by several different group names but each group
name repeats twice.

Example (this is how I want it to look)
Group 1
a a a
b b b

Group 2
c c c
d d d

Group 3
e e e
f f f

Each group name (ie 1,2,3) repeats on top of the next group's data so it
looks like this

Group 1 (this is how it looks)
Group 2
Group 3
a a a
b b b

Group 1
Group 2
Group 3
c c c
d d d

Group 1
Group 2
Group 3
e e e
f f f


Thanks for all help!