Prince Harry's Family Blindsided by Meghan Markle's Dad Deciding to Bail on Wedding

Kensington Palace was caught flatfooted by TMZ's story that Meghan Markle's dad will not walk his daughter down the aisle ... because we found out the palace had made elaborate plans for him.

Our palace sources say the plans included a security detail for Thomas Markle, along with accommodations and access to various events.

TMZ broke the story ... Thomas Markle told us he would not attend the wedding because he felt shame that he made a deal with a paparazzi agency that photographed him in staged shots.

One source connected to Meghan confirms what we posted Monday ... that Meghan's mom is now the frontrunner to give her daughter away. We're told the 2 are extremely close.

As for who's not close to Meghan ... her half-sister, Samantha Grant. Our Meghan sources say the 2 have "absolutely no relationship" and "she knows nothing about Meghan's life." The sources warn that Samantha is trying to take the media for a ride by planting stories with no basis in fact.

Finally, we tried to find out if Meghan has reached out to her dad to see if she could change his mind. So far, no word back.