Lewis, aged 13, is living on borrowed time because he suffers from a condition which means doctors did not expect him to live beyond the age of 12.
But when dad James announced he was marrying fiance Emma, there was only one person he wanted to be his best man - Lewis. His step sister, Poppy, was bridesmaid
The couple are having a legal ceremony next year in Portugal - but they have just held a special pre-ceremony with Lewis at the home in Bessacarr he shares with his mum Samantha Tolmie.
James and ex-wife Samantha split in 2008, when Lewis, who suffers from a recently discovered variant of the terminal illness Batten Disease, was four.
But the couple remained friends and Samantha regards Emma and her daughter as part of the family.
Although he is unable to speak because of this illness, Lewis 'delivered' speech with a little help from his mum, who had arranged a computer voice simulator to read a pre-written speech.
The computer program was designed to deliver a speech using the Yorkshire accent of a boy aged 10.
And there was not a dry eye in the garden as Lewis' speech was made.
Proud mum Samantha said: "It was brilliant. The speech had the effect we thought it may, and I think it is fair to say everyone cried.
"I wrote it on behalf of Lewis and it was played over the speakers in the garden. I listened to it 100 times and each time I cried me eyes out."
"Lewis really enjoyed seeing his family and friends - we even had an aunt come over from Australia.
"It was too much for him to be out there all day, but he was out there for a couple of hours. He loved seeing Emma in her wedding dress and Poppy in her bridesmaid dress.
"He was a bit in awe during the actual wedding. He carried the rings on his lap, and Poppy handed them over to James and Emma. Lewis had chose the rings by looking at them
"James and Emma had a wonderful day.
"But it was really sad knowing the reason behind what we were doing, as we don't know of Lewis will be here when they get married,. We don't know if he will be here even at Christmas.
"It was a really special day. I am always proud of Lewis. He is often in pain but still shares his laugh and smile, which lights up a room ."
Lewis has already confounded the experts by reaching 13.
He developed normally until he was two, walking and talking. Then one day he began limping. He lost the use of his legs, then his arms, then he couldn’t swallow.
He is on a ventilator and is prone to epilepsy and respiratory disease. He can no longer walk, move, or speak.
But Samantha says he can communicate with those who love and care for him using his eyes.
Lewis' speech told how his family had thought he would be a great sportsman like his dad before Batten's Disease struck him.
He said: "Daddy, thank you for being such a fun loving Daddy who has supported me through so much. Emma thank you for being such a beautiful bride and an extra-special step-mum. Poppy, thank you for being my little sis. I just want to say something my family has never heard me say. I love you Daddy and Emma. I love you mummy with all my heart. I love you Samuel and Poppy. I love you granny and grandad."
"I love all my family very very much.
"Congratulations - I hope I can be here for wedding number two."