The Data Model Resource Book, Vol. 1: A Library of Universal Data Models for All Enterprises

This is not a great design.

You should read up on the Party Model, and Table Inheritance to see a design built to last. A skeleton:

PARTY
id

ORGANIZATION : PARTY
name
doing_business_as

INDIVIDUAL : PARTY
first_name
last_name

PARTY_RELATIONSHIP
from_party_id references party(id)
to_party_id references party(id)
from_date
to_date

ORGANIZATION_CONTACT_RELATIONSHIP : PARTY_RELATIONSHIP

If you're just looking for data models, I recommend the following books:

• The Data Model Resource Book, Vol. 1: A Library of Universal Data Models for All Enterprises
• The Data Model Resource Book, Vol. 2: A Library of Data Models for Specific Industries
• The Data Model Resource Book: Universal Patterns for Data Modeling

I have Vol 1 and Vol 2 and these have been pretty helpful in the past.

I find the Data Model Resource book to be a good source of inspiration for modeling business structures. Apache Ofbiz ERP was built around the concepts in this book.