This isnt my litter but my wifes friends litter im asking about.The sire was one she travelled quite far for and she plans to keep a pup for the ring,it was planned for quite a while.Her dog was mated on day 9 and 11 then 5 days later her own stud dog managed to get to her while her son was watching the dogs.She decided to go ahead with the litter and just dna test the pups which she is yet to do  there is one pup in the litter that is the double of her own stud nothing like mum or the other sire but that would mean pups were born on day 56 is that possible? going by the other dates they would be around day 61.The dna test when done will answer the question but til now has anyone had a situation like this or pups born on day 56.Thanks

I have a litter at the moment that was born day 55 from first mating. (Just -it was literally just a couple of hours past midnight so almost still day 54.)

I have a breed that thinks day 56 is perfectly normal.  Pups totally viable and I've never had a problem.  I've never had a bitch go to day 63.

Some years ago my litter of 6 were born on day 56, all were perfectly well and thrived. No experience of the other part of your question though.