Kevin Federline's Attorney Says Britney Spears' Kids Support Jamie

The war of words between Britney Spears and ex-husband Kevin Federline is raging on ... and now his attorney says their teenage boys are backing Jamie Spears.

K-Fed's lawyer, Mark Vincent Kaplan, responded to Britney and new husband Sam Asghari's weekend attack on Kevin, telling a photog outside Craig's in WeHo Sam doesn't know what the hell he's talking about.

Britney's ex claims their two kids, 16-year-old Sean Preston and 15-year-old Jayden James, are avoiding their mom on purpose ... and Kaplan says the family member they really miss is their grandfather Jamie.

Brit's boys supporting Jamie creates an interesting family dynamic here ... there's clearly a wall between them and their mom ... and Kaplan makes it sound like the boys will see Jamie before they see Britney, despite a restraining order against grandpa.

Remember ... Kevin ignited the back-and-forth when he did a recent interview with DailyMail, a portion of which was posted Saturday, where he claimed Britney's kids haven't seen their mom in months, skipped her wedding to Sam and are put off by her partially nude social media posts.

Britney and Sam fired a return salvo, ripping K-Fed for talking about her relationship with her kids in public and claiming he's out of work and living off child support payments.

Kevin's attorney took issue with Britney and Sam's coordinated attack ... he claims K-Fed and his wife Victoria work 24/7 to keep Sean and Jayden out of the limelight and says there's no negative words against Britney or Sam in Kevin's household.

Kaplan says Britney should appreciate how much time Kevin logs being a parent and refutes the notion K-Fed is out of work, though he doesn't say what his job is outside of being a full-time dad.

While Kaplan says Sam just doesn't know Kevin well enough to attack him, he says K-Fed understands Sam is Britney’s new hubby, which means Sam is not going to take a position against her.