
None of your boys siblings or half siblings have been bred from.
Looking at his mothers mother and his farther the only descendent that has had a recent litter is MAKENZIES BRIGHT BLUE STAR AT CHERISHPORT, she had a litter last year. Is related to your dog threw both his grandmother bred to his farther (Heathromas Girl bred to Popeye The Sailor Man) then 3 gens later (A daughter, a son then a daughter). However this bitch hasn't any health testing listed at all. Something which seems a common theme threw out the lines.
Looking at your boys mothers father's descendants for litters in the last 2 years That have Affixes.
KENZDUO LADY WAFFLE, Both puppies have the RIRILEGACY affix. Again no health testing listed.
HYFRYDLAIS GIN. No health testing listed.
KENXTWEN PRETTY PENTATHLON AQUASPANGLES - had a litter 2023 and she has had some DNA testing, The litter was under the AQUASPANGLES affix
There are likely others I've just ran out of time and there was still quite a few litters to keep checking if they were bred on from. But you can trace it yourself by putting his name into the KC Health test finder then go to the bottom of the page where it lists his litters and go threw each litter in their own tabs and keep repeating the process until you get to a descendant that has a recent litter. To find out who bred them if they don't have a breeders affix will be harder and you would need a copy of the breed record supplement.
https://www.thekennelclub.org.uk/search/health-test-results-finder/For the health testing Cockers should be Hip Scored, Eye tested and DNA tested FN, AON, AMS, PRA. If it was me in not want to get a puppy from untested dogs