Karen Davey, 41, feared her kids faced life “without a mother” before she made the online plea for a donor.
Gary Summerfield, 60, said: “I saw Karen’s appeal and she mentioned the children, and I thought ‘Karen’s a similar age to my daughter and her youngest child is the same age as my grandson’, and I just thought it’s terrible for the children.
Kidney donor Gary Summerfield, from Tredegar, and his wife Mandy (Image: Wales news service)
“If It was my daughter, I would be searching everywhere if we had exhausted all avenues through the family and friends, I would want a stranger to come forward. And I thought it would be selfish not to.
“And she’s a very deserving lady and a deserving family.”
Security guard Gary, of Tredegar, and Karen, of Brynna, near Bridgend, underwent successful six-hour surgery in July, leaving her feeling “100 times better”.
Mum-of-four and grandmother-of-one Karen previously underwent a heart transplant after suffering a heart attack while watching her son play football.
Kidney donor Gary Summerfield, from Tredegar, and his wife Mandy (Image: Wales news service)
The medication Karen was forced to take following her first transplant increased the risk of kidney failure.
She was in stage three kidney failure and on kidney dialysis for four hours a day, three days a week, when she began running out of options to find a suitable donor.
Karen had approached family members and friends but because she had a rare blood type could not find a match.
She then turned to Facebook and Gary eventually saw her post.
Kidney donor Gary Summerfield, from Tredegar, and his wife Mandy (Image: Wales news service)
She said: “A message popped up from Gary who was a complete stranger to me. He said ‘I’d like to help you.’ I was blown away that someone who didn’t even know me was prepared to give me one of their kidneys.
“He had to go through 14 months of gruelling tests to ensure he was a match. There was so many tests before he donated his kidney to me. It was so selfless of him.
“For somebody to put their body through that and having a kidney taken out for somebody that they don’t know, it’s mind-blowing, I’m just so grateful.
Kidney donor Gary Summerfield, from Tredegar, and his wife Mandy (Image: Wales news service)
“There are no words, nothing I could do or say, to repay Gary for what he has done for me and my family. I’ll forever be grateful to him. He’s truly wonderful.”
Karen’s husband Matthew said: “Everyone knows what’s going on in the world at the moment, it’s a horrible place at times, but it really does give you hope that there is kindness in the world.
“We’ll never, ever be able to repay Gary and the family for what they’ve done, and to give Karen another chance, another chance of being able to be the mother to our children and just live a life that she deserves.
“He has given that gift of life.”