SQL statement

[coince]

I am using the following SQL statement to create a table and upload data using atxt file.
CREATE TABLE family (
person_id NUMBER (4) CONSTRAINT person_pk PRIMARY KEY,
Fname VARCHAR2 (20) NOT NULL,
Mname VARCHAR2 (20) NOT NULL,
surname VARCHAR2 (20) NOT NULL,
sex VARCHAR2(1) NOT NULL,
dob DATE NOT NULL,
death_date DATE,
father_id VARCHAR (4) CONSTRAINT bperson_fk REFERENCES family(person_id),
mother_id VARCHAR (4) CONSTRAINT aperson_fk REFERENCES family(person_id));

Once the data loaded this error message shows for each failed row:
ORA-02291: integrity constraint (USER1.BPERSON_FK) violated - parent key not found??
I cannot figure out the problem
Help welcome