Bi-directional needs to be there, and both needs to set for saving keys and data.
@OneToOne needs to be in both entity.
Owner of relationship - needs to have @JoinColumn and it's second partner will need to have @mappedBy(parent's variable).
If @ManyToOne annotation is owner of relationship(FamilyMember) - it will have @JoinColumn, the second partner will have @OneToMany with mappedBy=parent's variable.