When their family pet St Bernard fell pregnant the Batemans were expecting a normal litter of about six puppies.
But during an eight-hour labour, first-time mum Poppy produced a bumper crop of 13 healthy youngsters.
Now the family from Hankham, near Pevensey, are getting to grips with caring round the clock for a baker's dozen of six-week-old pups.
Angela Bateman, who has five children aged five to 23, said the huge litter was a complete surprise as only three pups were visible when the vet did a scan.
She and husband Alan, who own both the puppies' parents, have not bred dogs before and said the mating was a happy accident.
A 14th puppy was stillborn but Poppy and the surviving nine boys and four girls have defied the odds and are all healthy and thriving.
Mrs Bateman said: "Anything over eight is a large litter. To end up with 13 alive is quite a challenge. There is always a risk with first-time breeding but she has not rejected them. She's been such a good mum."
The family aim to keep the pups for two weeks, then sell 11 if they can find enough good homes.
They were born through the night in March. A friend helped the family deliver the pups and ease out a couple who got stuck.
Mrs Bateman's sons Adam, five, and Connor, seven, were woken up to see the first puppy born and eventually stayed up most of the night. There were no problems with the birth at all and all the puppies were thriving from the start - except for the last.
The dogs, famous for their mountain rescue role in the Swiss Alps, can grow heavier than an adult human. Mum Poppy is 12st and dad Alfie, aged two and a half, is 15 to 16st.
Mrs Bateman said: "They can be strong and powerful, that is what they're needed to be, but they are gentle giants. They are so soppy most of the time. They are very much family pets."
The puppies have just moved from their mother's milk to semi-solid food.
They have been cared for with the help of Highcroft Veterinary Group.
Anyone interested in giving a permanent home to one of them can visit Highcroft at 25 London Road, Hailsham, or 1 Mill Fields, Station Road, Polegate.
Has one of your pets had a huge litter? Leave your comments below.
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