You can create multiple table occurrences of the same table in order to create a relationship that links a table to itself. You can create a duplicate occurrence of an existing occurrence in manage |database|relationships by selecting it and then clicking the duplicate button (two green plus signs).
This can give you a many to many relationship with a join table such as this:
Personnel----<Join>----Personnel 2----<Join>-----Personnel 3
Each join table needs a minimum of two foreign key fields. The most basic relationship whould look like this:
Personnel::PrimaryKey = Join::ForeignKey1
Personnel 2::PrimaryKey = Join::ForeignKey2
Note that a third field in the Join table can be used to identify the type of relationship being defined by that field.
Thus, a field in it could be labeled "mother", "brother", "friend", "Parent", etc...