INDEPENDENCE, Ohio -- When Cleveland Cavaliers coach Tyronn Lue gazes down the sidelines during the Eastern Conference finals against the Boston Celtics, there will be another familiar face besides former Cavs guard Kyrie Irving looking back at him: his cousin, Jayson Tatum.

The Celtics rookie, whom Lue calls "Little Jay," is from St. Louis, about a two-hour drive from Lue's hometown of Mexico, Missouri. Lue and Tatum's father, Justin, are cousins on Lue's grandfather's side of the family, according to the Cavs coach.

The 20-year-old Celtic, who's in his first season out of Duke, has been spending time with Lue for more than half of his life. Outside of being blood relatives, Tatum's father and Lue share a mutual friend in St. Louis native Larry Hughes, the former Cavs guard.

"They come to Mexico all the time," Lue said. "Just seeing Little Jay when he was 6 or 7 years old and now to who he is today is crazy. Seeing the player he's become, we knew he was going to be good, but now he's at a whole new level. Just seeing him coming to Mexico and just coming to my barbecues and all that stuff and now he's an NBA player and playing at a high level, it's just good to see."

Tatum has scored 20 points or more in seven straight playoff games, passing Larry Bird's rookie record for the Celtics (four straight games) while also becoming the youngest player in league history with such a scoring streak in the playoffs, passing Kobe Bryant.

"He's playing exceptionally well for a rookie," Lue said. Justin Tatum texted Lue this week to make plans to see his cousin while he's coaching against his son during the conference finals.

Lue said the matchup will be "weird" to manage, but he will place his allegiances with his Cavs family over his blood family.

"It's tough because you want to see him do well, but not against you," Lue said. "We just have to, just try to take him and be physical with him and not let him get easy baskets. He's going to score because he can post and he can put it on the floor, but we just have to try to take away his easy baskets as much as possible."

Lue said he first believed Tatum had pro potential when he was "14 or 15" years old.

When Tatum was around that age in 2012, he tweeted at LeBron James asking for a follow back and included a photo that he and James had previously posed for together.

@KingJames Follow back it's Larry Hughes nephew from st. Louis and Abe and Rj Lil cousin and Justin Son Follow Back pic.twitter.com/AnOnb7E8 — Jayson Tatum (@jaytatum0) April 13, 2012

In the photo, Tatum is wearing a replica Bryant jersey from the 2006 All-Star Game. When showed Tatum's old tweet for the first time on Thursday, Lue shook his head and said, "Now look. That's crazy."

After being guarded by Toronto Raptors rookie OG Anunoby for the majority of the conference finals, James declared that the 2017 NBA draft class -- which includes Tatum, Anunoby and Rookie of the Year contender Donovan Mitchell (Ben Simmons was drafted in 2016, but is also considered a strong ROY candidate; he missed the entirety of the 2016-17 season because of injury) -- was the best draft class since James entered the league with his heralded group in 2003.

Tatum is averaging 18.8 points on 45.9 percent shooting, 4.5 rebounds, 3.2 assists and 1.2 steals in the playoffs after putting up 13.9 points on 47.5 percent, 5.0 rebounds, 1.6 assists and 1.0 steals per game in the regular season.

"He's not scared, he's not afraid and he's always been that type of kid," Lue said. "He wants these type of moments and he's taking advantage of it. With Kyrie (Irving) and Gordon (Hayward) going down and him having a chance to play the minutes he's been playing, starting and playing in the playoffs the way he has, he's taken full advantage of it. But he's never been scared, he's never been afraid of the big moment. You can see that."

Lue added that Tatum's toughness is the 6-9 forward's greatest quality, along with his control.

"As a little kid he was fast, but I think as he got taller it slowed him down a little bit," Lue said. "I think that has helped his game a lot. He's never in a rush, he plays patiently and reminds me a lot of Paul Pierce when Paul first came out. Being able to get to the free throw line, great footwork, never gets sped up offensively so he's a really good player."

Does Cousin Lue take credit for Tatum's success? "No. No," Lue said with a smile. "He got it from himself and his dad."