EXCLUSIVE: Paris Jackson's Co-Guardian TJ on Her New Boyfriend: 'I Keep a Close Eye on Him'

Brothers TJ, Taj and Taryll also give an update on grandpa Joe Jackson's health.

Paris Jackson is (almost) all grown up!

The 17-year-old daughter of the late Michael Jackson made headlines in May as she hit the red carpet with boyfriend Chester Castellaw, 18, a soccer player for the Real So Cal youth soccer club. Now Jackson's co-guardian TJ Jackson, son of Tito Jackson, is giving his take on the budding romance.

"I approve of him," TJ tells ET. "No one's perfect, but he's a good boy, so I approve of him... He treats her well. She's happy."

WATCH: Paris Jackson and Her Boyfriend Make Their Red Carpet Debut

Still, 37-year-old TJ is definitely keeping a watchful eye over the teen lovebirds.

"It depends on which day you ask me," he admits. "He's a good kid. He's an ambitious kid, you know. He's a teenage boy, so like any parent, guardian, step-parent or adopted parent, you gotta keep an eye on him. I was a young man too once, so I keep a close eye of him."

ET was with TJ and his brothers Taryll and Taj -- who together make up the R&B-pop trio 3T -- on Thursday during a visit to the set of their upcoming Lifetime docuseries, The Jacksons: Next Generation, which will premiere on Oct. 2.

WATCH: Janet Jackson Shuts Down Tour Production to Be With Her Father

The brothers also gave a health update on their grandfather, Joe Jackson, who suffered a stroke on his 87th birthday, July 25, in Brazil.

"He's doing better," Taj says. "It's hard because [at] a certain age you start [to] cherish all the times that you have with them and stuff like that…He’s just such an important point to this family as well. I sometimes think he doesn’t get the credit that he deserves, but I’m so thankful for what he did for our family."

As ET reported last month, Janet Jackson had put her tour prep on pause to be by her ailing father's side, while Joe Jackson posted a message for fans on his website.

"To my family, friends, acquaintances and fans all over the world. I want to thank you all for your prayers, unwavering support and kind well wishes during these trying times," he wrote. "Through God's intervention the wonderful Doctors, Nurses and caretakers at the Albert Einstein Sao Paulo hospital have taken great care of me. God willing, I should be able to make a quick recovery and travel back home soon. Thank you all once again for your prayers and support."

According to the Associated Press, Joe Jackson was released from the Albert Einstein Hospital in Sao Paulo on Monday.