The Manchester suicide bomber was motivated to kill by the deaths of Muslim children in Syria — which he believed came at the hands of US-led military forces, a sibling says.

Salman Abedi, 22, was trying to quench his thirst for revenge when he blew himself up at the end of the Ariana Grande concert on Monday night, according to his sister Jomana Abedi.

“I think he saw children — Muslim children — dying everywhere, and wanted revenge,” she told The Wall Street Journal on Wednesday.

“He saw the explosives America drops on children in Syria, and he wanted revenge,” she said. “Whether he got that is between him and God.”

Abedi killed 22 people and wounded scores more when he detonated his explosive device inside a packed Manchester Arena, just as concertgoers were heading to the exits.

A family friend told the Journal that the young man had been fueled solely by vengeance — and that he was determined to send a message to the world following the death of his 18-year-old pal, Abdul Wahab Hafidah, who was murdered in Manchester last May.

“I remember Salman at his funeral vowing revenge,” the friend explained, adding that over time, Abedi became more and more religious.

“We knew he was going to cause trouble,” they said. You could see that something was going to happen, sooner or later.”

Neighbors told the Journal that Abedi tended to walk around his neighborhood with his siblings, wearing traditional Muslim dress, despite the fact he wasn’t a regular at the local mosque.

While his sister claimed that Abedi saw children dying in Syria, his father, Ramadan Abedi, reportedly said in an interview with police that he had never actually been there before.

“We don’t believe in killing innocents. This is not us,” the dad said, just before being detained Wednesday in Libya.

Abedi’s older brother, Ismail, was also taken into custody, along with his 18-year-old brother, Hashim.

The younger sibling reportedly confessed to being aware of his brother’s plans and told police that he was acting on behalf of the Islamic State.