Littermates tend to be rough with one another, but you can't let a 6 week old do this with a 14 month old as noted above. Too dangerous. You do have take the role of the mom doggy and teach your pup boundaries and bite inhibition.
I brought my 2nd Yorkie home when he was 8 months. He wanted to wrestle his adult Yorkie brother a lot. When things got out of hand, I raised my voice "Nooo!" and clapped my hands. I taught the boys keyphrases like "settle down."
Nipping at the neck is fighting. My boys will still snap mouths at each other when they are overly excited. I redirect them to something positive like playing a few minutes of fetch or doing tricks for treats.
We also had to do a little separating with the xpen and baby gates in the first couple of months.
I highly recommend using positive reinforcement training with non-physical corrections. When I tried the latter, it only hyped up the pup.
__________________ Kristin, Max and Teddy  |