A Brooklyn teen accused of fatally stabbing his dad is a good kid pushed to the brink by an abusive father who had been molesting one of the boy’s sister’s, neighbors and prosecutors said Sunday.

“The son is a good son. He was getting beat every night,” a neighbor named Bobby said of 19-year-old Hassan Razzaq. “This was a tragedy waiting to happen. The neighborhood knows about it, the police officers know about it, everybody knows about it.”

“I don’t feel one bit sorry for the victim. That’s how sad it is,” said Bobby, who lives across the street. He would give only his first name.

Razzaq was arrested Saturday night for allegedly plunging a kitchen knife into his 56-year-old father’s throat at their home on East Third Street in Kensington.

Mohammad Razzaq was discovered by cops lying face-up in the living room at around 10 p.m. by police responding to a report of an assault, officials said.

“[Hassan] came running out. I said, ‘What’s the matter?’ He said, ‘Bobby, please don’t get involved. Stay out of it.’ I said, ‘What did you do?’ And then he just took off,” the neighbor recalled.

Hassan Razzaq was charged with murder and criminal possession of a weapon. He was held without bail, as his family sat stoned-faced in Brooklyn Criminal Court.

Hassan had recently learned that one of his sisters had been molested by his dad for years, a prosecutor said.

The father had just come back from Pakistan and the teen feared that another, 15-year-old sister would become the next victim, said ADA, Tziyonah Langsom.

Cops said they had been repeatedly called to the house in the past to handle disputes involving Mohammad Razzaq and his family. The father lived at the home with his wife and five kids, who range in age from around 9 to 21.

“The guy was an animal,’’ Bobby said. “I told [him] six months ago, ‘If I find out you’re beating your wife and kids up there, I’ll come in there and beat the s–t out of you.’ This is how bad it got. Most people here know, [but] they don’t want to get involved. I think it came to the point of no return.

“I will go to court for that boy [Hassan],’’ the neighbor added. “He needs to be punished, but they’ve got to be lenient.”

Another neighbor, Gissette Vasquez, said she saw the son after the slaying, and “he don’t say anything, but he looked scared.”