Justin Timerlake and Lance Bass go all the way back to the ‘NSync days–meaning they’ve known each other since the 1990s. Bass recently spoke out about strong changes he’s seen in Justin Timberlake. And he credits just one person for those changes.

The two ran into each other when Justin was filming his appearance on The Tonight Show With Jimmy Fallon earlier this week. That’s when he first noticed the changes in his old friend.

“It’s been five months and it’s so amazing to see a friend go through this, because you know, I grew up with him since he was 14 years old,” Lance Bass said of Justin Timberlake. “But to see this amazing dad now… all he wants to talk about is the kid.”

The person Lance Bass claims has initiated the biggest changes ever in Justin Bieber is his baby boy, Silas Timberlake.

Now surely, Lance would agree that wife Jessica Biel has helped the “D*ck in A Box” singer make some positive changes, too, but it’s that baby boy who gets most of the credit.

Bass shared an Instagram shot of his meet-up with Justin Timberlake earlier this week.

“Well well, look who’s in the #NBC house today! @JustinTimberlake and Cousin Rachel! Catch JT on @jimmyfallon,” he captioned it.

A photo posted by Lance Bass (@lancebass) on Sep 9, 2015 at 10:03am PDT

While chatting with Jimmy Fallon on The Tonight Show, Justin Timberlake pulled out some recent photos of baby Silas. The Tonight Show shared them via Twitter so all the home viewers could get a close look as well.

Whoa, baby! @JTimberlake shares some pictures of his new son https://t.co/Tm6CHM545H pic.twitter.com/5fYxDLJ2Fa

— Fallon Tonight (@FallonTonight) September 10, 2015

“[He’s] completely changed and you have to,” Bass said of Timberlake. “I mean I can’t wait to be a dad myself just because I would love to know what that selflessness feels like.”

Lance Bass also said that he and husband Michael Turchin have a plan in place for eventual parenthood.

“One of the reasons I wanted to marry him was because I want to start a family, and we definitely in the next two or three years want to start that family,” he dished. “I know people are very on the fence with IVF and all this stuff, but people have been doing it for years. With us, of course we want to find a surrogate to have our own kids, but now I was just reading with stem cell research and all this, and that’s of course up to the minute, now they are saying with the skin cells of a male you can actually produce an egg and fertilize [it], so you can have biological kids with two males.”

Regardless of which method Lance Bass and his husband choose, Justin Timberlake will likely offer a few pointers about being a great dad.

Do you agree with Lance that fatherhood has changed Justin Timberlake profoundly?