I think this is a common problem with young puppies. You must remember that 12 weeks is still very young for a puppy. I know from personal experience that when you have several siblings of this age they are especially aggressive. Without a mother’s guiding hand, they do not receive the specific ‘tellings-off’ that only a mother’s communication can bring. Perhaps a lot of people would tell you to be patient, but I know of an old trick that sheep-dogs and guide-dogs are subjected to to stop them from attacking sheep in the open field.

You will need something similar to a Thermos flask and some gravel. Every time your dog tries to bite you or your other dog, you should throw this flask (filled with a little gravel) at the ground near him. Be very careful not to hit him. This should, if properly carried out, make him associate this single behavior with a very scary noise. The great benefit of this is that over time you can replace the throwing of the Thermos with a simple rattle. If, however, he still appears to be too anxious after the initial shock has worn off, you should discontinue use. This can then be used for other behavioral problems. Another suggestion would be to use a strong whistle instead of the Thermos flask. We wish you luck!