On RealOffice360 we have built it in such a way that you have a primary contact and attached family members. The primary contact is the name you see in the Database, while you can add unlimited family members to each of these.
For example, if you were my client we would add you as a contact. Then we would click on your profile and click "Family". From here we could add all family members with notes and birthdays! We should also point out that these birthdays will appear in your calendar!
For more, you can check out or Learning Center here: Link to Family Info