Kourtney Kardashian is firing back at speculation she’s a grandma … blasting trolls online for spreading a rumor that her 15-year-old son is a teen father!

The reality television star jumped on Instagram Sunday to address internet speculation that her son, Mason Disick, has a kid of his own … saying she doesn’t usually address insane gossip like this, but felt she needed to step in for her child’s sake.

KK straight up denies the rumor … calling it a conspiracy and claiming many social media accounts pretending to be Mason are fake — and, they’re spreading lies about him.

Rachel Zoe says parents need to put their foot down when it comes to their kids riding electronic bikes … ’cause her son was hospitalized after a bad crash.

The fashion designer took to Instagram this weekend to share her son’s plight … telling fans her 13-year-old son Skyler ended up with a “badly lacerated kidney, a ton of pain and a shattered mom” after an e-bike accident.

Rachel adds that her kiddo is in pain when he laughs or sneezes … and, she says there’s no way she’s ever letting him anywhere near an e-bike again.

Zoe says any parent considering buying their kid an e-bike better think twice about it … ’cause they spent hours in the ER after the crash. Worth noting, Zoe makes a point to say she didn’t buy him the bike — but, somehow he ended up on one.

Unclear exactly how Skyler crashed … but, he’s not the first celebrity kiddo to end up in the hospital because of an e-bike accident.

Remember, Pax Jolie-Pitt slammed into the back of a car while on an e-bike over the summer, law enforcement sources told us … and, he reportedly ended up in the intensive care unit.

The crash was so bad, eyewitnesses said they thought Pax died. Thankfully, he was released from the hospital a few days later. He ended up crashing into ANOTHER car while on an e-bike in January — but, he apparently did more damage to that car than it did to him.

Big Time Rush is going on their own tour soon … but, they’re not above going back to being an opening act — for one big-time band that is.

We caught up with the popular boy band in Los Angeles Friday night … and, we asked them what reunion tour they’d most want to see — and all four of the guys say it has to be *NSYNC.

Kendall Schmidt, James Maslow, Logan Henderson, and Carlos PenaVega all say they’d love to see the early 2000s group get back onstage together … but, they think Justin Timberlake ultimately has to want to do it.

BTW … Big Time Rush has their own tour starting soon. The four main members will appear alongside Katelyn Tarver and Stephen Kramer Glickman, who both played major roles on the hit Nickelodeon show that launched BTR into fame — and, they held a pop-up event in L.A. to get fans excited.

We also asked the band about what the vibe of their tour is like … and, ya gotta listen to their answer for yourself.