Brandon Williams described himself as a “little chubby kid” who liked to be outside.

Basketball was just something he did to be active. He didn’t have a favorite player. He didn’t watch the sport. He wasn’t even on a team.

“It didn’t matter to me,” the Laurelton, Queens, native told The Post in a recent interview. “I was just doing it to do it.”

Around the eighth grade, that began to change. Williams started to lose his baby fat. He joined the New York Gauchos AAU program. He shot up in height. Still, he didn’t catch basketball fever until one day, when he got a chance to play in an NBA arena, Barclays Center.

“It kind of took off from that point,” his grandmother, Dawn Grubbs, said. “Him playing there really allowed him to see the potential. From then, he was at every tournament, every basketball game, every practice. He constantly had a basketball in his hand. Thanksgiving he wanted to go to the back of the building to shoot.”

Basketball became his life. Already, it has taken him pretty far.

Now 6-foot-9 with perimeter skills, Williams is a consensus top-100 recruit playing for Queens powerhouse Christ the King High School. The rising senior, who has a top-five list of St. John’s, Connecticut, UCLA, Oklahoma State and Illinois, is set to become the first male member of his family to attend college.

“I said the other day to my grandmother, ‘My life just changed in the blink of an eye,’ ” he said. “Everything was regular and out of nowhere, everything started skyrocketing.”

It obviously wasn’t easy. Williams had to sacrifice the life of a normal teenager, being in the gym when other kids his age would be hanging out. He developed a bond with CJ Steed, an assistant coach at Christ the King who was close to his family and was always there to find a gym for him. There were times Williams wanted to be a normal kid, but when he landed scholarship offers from LSU and TCU as a freshman, he knew there was the potential to do big things.

“It made me hungry,” he said.

This past season at Christ the King, Williams made a name for himself, averaging 15 points, eight rebounds and four assists per game. He recently earned a tryout with USA Basketball’s U-17 team. He has enjoyed a strong AAU season with the powerhouse PSA Cardinals, and has seen his name appear in top-100 rankings lists. Still 16, Williams is young for his class, unique in an age when so many basketball prospects reclass prior to high school.

“Put him in the sophomore class, [he’d be the] No. 1 player in the country,” Christ the King coach Joe Arbitello said.

A college coach familiar with Williams said he has the tools to be a two-way standout in college and possesses the versatility teams love in big wings.

“All-conference potential at the high-major level,” the coach said.

A few new schools, such as West Virginia and Georgia Tech, have tried to get involved recently. Arbitello believes Williams’ recent play has been an “eye-opener” for coaches regarding how high his ceiling is.

“You just see how comfortable he is on the floor, how fluid his motions are,” Arbitello said. “Then, they find out how old he is. … This kid could come back 7-foot his freshman year of college. You can see he still has room to grow.”

Williams has a huge month ahead of him. First up was the Peach Jam, the prestigious AAU tournament in North Augusta, Ga., this week. Then, he will make an official visit to UCLA in mid-August and he is hoping to visit Oklahoma State as well before making a decision near the end of the month.

Williams has already visited St. John’s officially and has taken multiple unofficial visits to the school. The Red Storm have made him a priority, hoping to pair him with recent four-star commit Brandon Gardner to form a potent 1-2 forward tandem. St. John’s fans have frequently reached out to him on social media.

“Just playing in my city, I know I’m going to have a different type of love,” Williams said. “Being home, all my support and my family, everybody, is just here. It’s easy for people to come to games. If anything is wrong, I have access to the people close to me.”

His grandmother said Williams would have up to 50 family and friends at home games if he opted for St. John’s.

Gardner and Williams have become friends. The two will be teammates this year at Christ the King, as Gardner recently announced his decision to transfer to the Queens school. Williams also has a relationship with former St. John’s star Julian Champagnie, who is now in the NBA with the 76ers after signing a two-way contract. Like Champagnie, Williams is very close to his family, and the two talked about the bonus of staying home for college.

“He just told me, I know what the move is,” Williams said.

Ultimately, he said, his decision will come down to comfort and his relationship with the school’s coaching staff.

For now, Williams is focused on finishing the AAU season strong. No matter where the skilled forward opts to attend college, he will be accomplishing a goal he set out to reach years ago. He will play high-level Division I basketball and set the standard for males in his family.

“Being from where I’m from, not many kids are able to do the stuff I’ve done,” Williams said. “It’s like a dream come true, for real.”