I'd say jimmy is bang on but its also true of any pups of a similar age not just litter siblings, any pup will always have to be trained seperately but it does double ur time and will most likely need to be walked seperately until good at walking to heel on a lead, with 2 or more very likely to start pulling even when then dont pull on there own.
Possible if u have the time and the set up to do it.
if it was me i'd try to keep the pups apart but 1 FT spaniel lad i know set up a puppy creche and all his young pups are in 1 big communal run, althou all trained seperately obviously, but he could be taking on anything up to10+ pups a year.
So possibly it doesn't matter that much if trained seperately or mibbee different with so many pups together don't form a strong bond to only 1 pup??
U also have other things to think about, introducing 2 dogs to the field at the same time
Having 2 dogs of the same age, so when they get older ur losing 2 dogs at the same/similar time, if u always need a trained dog/s it means u soon have a few dogs about u if u already have a middle aged dog in its prime under them and a pup coming on too, u might still have a retired dog hanging on aswell
U can quickly fill a kennel never mind a house
With 2 related dogs from the same litter u always have the chance of some freak genetic condition showing up even with health tests, heart murmor, cancer, epilepsy etc, if another owner also phones u to say his pup has the same would u really want to breed of the healthy pup from the same litter?
While it may be 100% healthy it could be a carrier that would continue in ur lines.
The above is quite unlikely but could and does happen sometimes
