Multiple person roles in database(how to define if same person)
The Name of a Person and his/her Bith Date are almost enough to make an unique index with both columns. This way you would garantee 100% of unique individuals in your table, but you could have problems with those miracle situations where two people born the same day with same name. 

In this case I would recommend you add a new columns called Birth place (City/State/Country) to your Person table and make the Unique Index with those 3 columns. 

It will solve your problem.

create unique index single_person_id on Person(name, birth_date, birth_place);