Ruby - You just asked the ten million dollar question ! I will try and keep this as short as possible - but it will be hard for me to do .
After we lost Chi - we waited 9 years to get another Doberman - it just broke our hearts when we lost her , Then in 2000 , we got Kasia - we had always been a 2 dog family , Kasia was a Princess and the Queen of our house till 2009 , that is when we got Ali - it was a 4 hour drive to pick Ali up , so we took Kasia with us , On the way home - it was so sad - Poor Kasia was upset with that NEW puppy sitting on her mommy's lap , When we traveled - Kasia would lay her head on my wife lap all the way - Not that trip home that day - she turned around and looked out the window all the way home - would not look at her new sister . We had turned the garage into my office and a everything room - All of Kasia's balls were kept out here , that night - when we were holding little Ali girl - Kasia walked out , looked at us loving on the baby , turned around and took all of her balls to the back bed room - one at a time , till she had them all in there , lets say - she had to make many , many trips . That NEW puppy was not going to play with HER stuff .
It took 2 full years for Kasia to accept Ali , and they became best of friends - Ali was never mean to her , not once , then in 2015 - we lost our Kasia girl - Poor Ali cried and cried for her .
Then I told the little lady - we were not waiting very long to get another Dober , by a stroke of luck and knowing the right people - we got Kadin , Now the shoe was switched and friend - That did not turn out well either - even as Ali was younger than Kasia was when we brought Mr. Business home - it was not good - Her feelings were hurt - much like Kasia's were . I will say that it did not take long before they were playing and having fun - but Miss Ali sure would put him in his place - Not all her fault - he would ding dong her to no end then here he came running to dad after Ali gave him a attuite adjustment .
We Lost Ali girl last fall , before long it will be a year , Kadin took it very hard , I never seen a Dog morn as bad as him - He would take one of her balls to her grave , sit it down , then walk back 10 feet or so and lay down and just watch - Hoping she would come get her ball . Like last time - I got on the phone to our breeder looking for a new little girl ,it just takes time , and this past Sunday -I picked her up - I had no doubt that he would be just fine ( Kadin is 5 ) and happy to have a new dog to play with ------------------------------- WRONG ! He just don't understand why or who is in here , he has done , pretty well , but he hates it when I hold her , he turns his head and won't look at me , this morning when I walked into the house holding Evie - he was laying on the couch , as soon as I walked by him to pet him , he jumped off the couch , walked around the back and laid down , Now my wife can hold her and he will lay right next to her and Evie But not dad ! We are the very best of friends , and I hurt him .
So after this long winded reply - I am pretty sure that they will be friend ------- Someday - how long will it take ? I have no idea , but they will . Just be prepared - from all our dogs we have had - the dog at home will get his or her feelings hurt , anyway that's how it played out here .
I will also add that I have to wonder if age - no matter what it is , young , old , if it really makes any difference - the dog at home , I feel , will always be affected
Just some of things we have seen here on the farm
Best of luck