There are (at least) two issue here. First you need to find the proper criteria to select persons. Second is you want to show the role of a person. To solve this I think you need a UNION query. Something like (NOT tested):
Code:
SELECT *, "Person" AS Role FROM PersonTBL WHERE PersonID = Forms!PersonFRM!PersonID
UNION
SELECT *, "Mother" AS Role FROM PersonTBL WHERE PersonID = Forms!PersonFRM!MotherID
UNION
SELECT *, "Father" AS Role FROM PersonTBL WHERE PersonID = Forms!PersonFRM!FatherID
UNION
SELECT *, "Brother/Sister" AS Role FROM PersonTBL WHERE MotherID = Forms!PersonFRM!MotherID AND FatherID = Forms!PersonFRM!FatherID AND PersonID <> Forms!PersonFRM!PersonID