What I would do is to create a new table in the database that stores the names of the groups and a list of members. For example (assuming mySQL for data types):
CODE
______________________________________________________
| group_name VARCHAR(#) | members BLOB |
|-----------------------|----------------------------|
| cool group | personA, personB, personC |
|-----------------------|----------------------------|
| not as cool =( | personR, personD, personQ, |
| | personF, personJ |
|-----------------------|----------------------------|
| etc. | etc. |
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Then when you need to access the members of the group, you could get the blob and explode it at ", "
You could also have a cell in the members table that keeps track of which groups each member is part in the same fashion.
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