triggers vs b-tree

[gustavo halperin <ggh.develop@xxxxxxxxx>]

Hello I have a design question:

 I have a table representing Families, and a table representing Persons.
The table Family have a row family_id as primary key.
The table Person have a row person_id as primary key and contain also a 
row family_id.
As you can understand, the row family_id in a table ficha_person is not 
unique, I mean is the same for all the family person's.

So my question is: If most of the time I need to find all the persons 
for one asked family what is the best way to do that?
I think about two methods:
        1-  Making a b-tree index in ficha_person with the rows 
family_id and person_id.
        2 - Adding an array in the table ficha_family containing the 
persons of this family. And creating a Trigger that update this array 
for each  person insert/delete in the table ficha_family.

So ..., what do you think? There are a better solution or what of the 
above solutions is better ??

 Thank you in advance,
          Gustavo.

Tables:

CREATE SEQUENCE ficha_person_id_seq;
CREATE TABLE ficha_person (
 person_id    integer         DEFAULT nextval('ficha_person_id_seq')  
CONSTRAINT the_pers
on_id PRIMARY KEY,
 family_id    integer         ,--CONSTRAINT the_family_id
.....
) WITH OIDS;


CREATE SEQUENCE ficha_family_id_seq;
CREATE TABLE ficha_family (
 family_id    integer         DEFAULT nextval('ficha_family_id_seq')  
CONSTRAINT the_fami
ly_id PRIMARY KEY,
 person_id   integer[],  --- Optionally, instead of using b-tree index.
.....
) WITH OIDS;