The Archbishop of Canterbury has discovered that his biological father is Sir Winston Churchill's last private secretary the late Sir Anthony Montague Browne.
The Most Rev Justin Welby, who believed his father was Gavin Welby, said the news has come as "a complete surprise".
In a statement, the Archbishop said the discovery did not change who he is because he says: "I know that I find who I am in Jesus Christ, not in genetics, and my identity in him never changes."
Mr Welby also revealed his "messy" childhood because of his parents alcoholism.
He said: "As a result of my parents' addictions my early life was messy, although I had the blessing and gift of a wonderful education, and was cared for deeply by my grandmother, my mother once she was in recovery, and my father (Gavin Welby) as far as he was able."
Gavin Welby died "as a result of the alcohol and smoking" in 1977 when the Archbishop was 21.
His mother, Jane Williams, has been in recovery since 1968, and has not touched alcohol for over 48 years.
Mr Welby said he did not think his situation was "unusual".
"My own experience is typical of many people. To find that one's father is other than imagined is not unusual. To be the child of families with great difficulties in relationships, with substance abuse or other matters, is far too normal", he added.
Mr Welby's mother has confirmed that she had "a liaison" with Sir Anthony but never suspected that he was the father of her son.
The Daily Telegraph said it persuaded Mr Welby to take a DNA test after 'piecing together evidence'.
The paper said mouth swabs were compared with hair samples from Sir Anthony and showed a 99.9779 per cent probability that they were father and son.