your son is timid of the dog . So he is already stressed , and then the dog gives him good reason to be frightened .
You bought an adult dog , without training , recently, and have not trained him , given him full freedom , while the son, the family are inhibited by the dog. Your son should be able to move around his house , wake up in the middle of the night to go to the bathroom without thinking about hazards .
You either crate the dog whenever he is not being trained, under supervision/control , until you know the dog and he knows his place -- or he goes back. I would opt for the GO BACK , no chances with dogs and kids .
Sounds like a distress sale in the first place . Why did the person sell the dog ?
Niko has been trained. He knows basic german commands. He obeys me the first time I tell him to do anything. The lady had teenage children but had a 5 and 8 year old niece and nephew that were frequent visitors. The reason she stated for getting rid of him was she was moving because of divorce and had 6 dogs. She had to get rid of all but two and was keeping the older dogs 9 & 10 yr old rescues.
Niko plays with my son with no problems, and when we are out at the park with him, he tries to keep Matthew nearby and will go towards him and "check on him", lick him and play with him.
Like I said this has happened on three occasions. I have had him for a little while. I do not leave them alone for one minute togather!! I would not. If I am not there he is crated. I also crate him at night. When this has happened I told him Nein! and he immediately layed down and stopped. I put him in his crate and left him for 15 minutes. I then let him out but ignored him for 5 minutes. After that I called him to me while I was holding my son in my lap and helped my son pet him. I kept my son sitting beside me with my arm around him while I talked to Niko and would not let him up on the couch with us.
I think that the growling is one of either three things:
1) He was keeping my son from going outside as he was laying in front of the door...he cries if either of my boys leave and he is left in the house. He will go from the front to back door then he will look out the window like he is listening for them. He is always making rounds through the house and checking on everyone and everything.
2) My son was sidestepping around him very slowly and staring at him. It could be that Niko thought he was challenging him
3) Maybe the niece and nephew was mean to him???
I am not sure and was hoping I could get some ideas on what I could do to build a relationship between the two. Neither one of my boys wants him to leave. My 5 yr old started crying when I mentioned it. He loves Niko and most of the time they are great togather. Just the three times. Since the last time when I did the above mentioned crate/ignore he has not had any futher episode. I just want to be sure that nothing happens again. I don't want to take any chances.
I am calling a trainer after the holidays as I am sure they will not be open before then. I thought I might get some suggestions until then.
Niko is a very smart GSD. It took me two nights to train him to automatically go into his crate and lay down when I tell him "Niko it's bedtime, go to bed". It only took me a day to teach him to keep his toys and bones in his basket. He puts up what he has out before he gets another item out. I feel like as smart as he is there HAS to be something that can be done. We all love him very much and want to keep him if at all possible.
I am sorry that I posted such a long post I just wanted to try to give a more accurate picture of what is going on.