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.
If you're just looking for data models, I recommend the following books:
I have Vol 1 and Vol 2 and these have been pretty helpful in the past.
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:
ORGANIZATION : PARTY
INDIVIDUAL : PARTY
from_party_id references party(id)
to_party_id references party(id)
ORGANIZATION_CONTACT_RELATIONSHIP : PARTY_RELATIONSHIP