KENDRA WILKINSON has escalated an already bitter family feud by banning her mom Patti from her only grandson’s 4th birthday party!

The pregnant 28-year-old reality star and former football-player hubby Hank Baskett, 31, rolled out the red carpet for son Hank IV and his pals at the Sky High trampoline park on Dec. 8 in Woodland Hills, Calif.

“It was noisy, crazy fun with snacks, pizza and a cute super-hero cake,” a source at the party told The ENQUIRER. “The kids had a great time bouncing away on the trampolines to the music. But the guests couldn’t help noticing that none of Kendra’s family members were there, particularly Patti and (her brother) Colin.”

The truth is that neither one was invited. Kendra and her mom haven’t spoken since mid-October, when the former Playboy playmate publicly announced she was expecting another baby – before she told her family the good news.

On Oct. 18, Patti posted a harsh rant on Facebook about the situation, accusing her only daughter of hating her.

“It’s turned into a nasty family feud,” said the source. The rift has forced Kendra to already miss out on Wilkinson family milestones and events, including her maternal grandmother Mary Stotz’s 89th birthday on Oct. 30 and Patti’s 55th birthday on Nov. 2. To add insult to injury, Kendra and Hank celebrated Thanksgiving at the Playboy mansion with Kendra’s ex-beau Hugh Hefner.

Now those close to the feuding mother and daughter hope they can mend fences before Kendra delivers her baby girl in the spring.

Grandma Mary wrote to her daughter Patti on Oct. 30, saying: “I sincerely hope life will be kinder to you in the future.”

But the source said Kendra’s snub was like a “knife to the heart of Patti” and that “it’s a terrible situation with no end in sight.”