The three-year-old boy had been in hospital following the crash which claimed the life of a girl.
A three-year-old boy has died after a crash on the M4 that killed another child, his family have said.
The boy had been in hospital following the crash last Saturday involving a car and a van on the motorway near Newport.
Four-year-old Gracie-Ann Wheaton died following the collision and a woman and man were also injured.
A 41-year-old man from Neath Port Talbot was charged with causing death by dangerous driving following her death.
A family member of the boy, who cannot be named for legal reasons, said: “The minute he walked in the room, he would light up the room.
“That is what is so sad. He was a loving, beautiful boy.
“He touched everybody’s heart. It’s heartbreaking.”
The family member added: “The mother is still in hospital – we wouldn’t wish this on anyone, we are stunned.
‘Not a dry eye in the valleys’
“It’s a sad time and it’s affected everybody. There’s not a dry eye in the valleys.
“The amount of people getting in touch has been incredible, amazing support. It’s amazed us all.”
The crash, between junctions 28 and 29, prompted a huge emergency services response and the route remained closed for about seven hours.