@Micah @rachael
A quick google search would provide this nuanced answer:
"Any endorsement may be lifted only with the permission in writing of the endorser or of a person with due authority from the endorser (in the event the endorser cannot give permission due to death or incapacity) or by resolution of the Kennel Club Board."
This is a resource for inquiring about making your request to the KC:
https://www.thekennelclub.org.uk/forms/application-to-lift-or-place-an-endorsement/
@rachael Again, I would continue an honest dialogue with your male's breeder, and see if you can come to a resolution together. At least try to reach out once more as you never know. Perhaps agreeing to contractually neuter your male to ensure a mis-step will never occur again could help this outcome.
These endorsements are in place for so many important reasons to protect the breed; not least to safeguard from unplanned puppies or BYB.
I'm hoping for the best outcome for these puppies.
And of course, do keep the forum abreast of the situation, and the details of the forthcoming litter. I'm sure you can find great placements on this forum.
Wishing you the best!