Shane, who was born in 2004, was the second-youngest of Sinéad's four children. Writing in her autobiography, Rememberings, she talked about how special Shane was.
"I remain very fond of the child's father, Dónal Lunny, although we are not close," she wrote.
"Things became very difficult for Shane and for me. Shane is an extremely special character, very, very psychic and very, very spiritualised.
"When he was three, he asked me one day, 'Were you in an earthquake when I was inside your tummy?' At first I said no because I forgot that I had been. When he was two weeks in my belly- didn't even know I was pregnant - I was on holiday in Malta, and there was an earthquake.
"I never thought about it again, I never mentioned it. I never told the child; I don't think I even told anyone else. Yet this three-year-old child was able to tell me I was in fact in an earthquake, and I don't know how he knew this."
She said another time when he was in the bath, he asked her if she had ever met God.
"And I said, well, maybe I did, some kind of magical things happened to me, and maybe I met God in certain ways. The child tut-tutted at me as the water was leaving the bath and said, 'That's not how you meet God,' he told me. 'You have to make your dreams come true'."
She said Shane was brimming with intelligence.
"Shane was assessed at age eight and declared a genius. I was told that he had the learning ability, the vocabulary, and the mathematical reasoning of a 16-year-old. He began to study science at a college with the adults in Dublin, but he didn't enjoy going there, so it didn't last long."
She said he reminded her of Clint Eastwood.
"He could get himself into all kind of trouble, but because he is so calm and so sweet and so genuinely charming, he manages to sail through things without them affecting him terribly badly, and I admire him for that.
"Shane is not a square peg to be shoved into a round hole.
"He is the child who is most like me, I believe, to look at and by his nature - although he is of course the version of me with logic and reason."
If you have been affected by the issues raised in this article, contact the Samaritans on 116 123; Pieta House on 1800 247 247 or text HELLO to 50808, a free 24/7 text support service for people going through a mental health or emotional crisis.