Thank you for that information. So it does sound like you are dealing with possession aggression which can escalate over time whenever any possession is in the area, even if neither dog wants it at the time, they will still want to possess it.
Your best bet is to start the learn to earn program with both dogs and put everything up, especially anything of value. Train the younger one on a daily basis in obedience so you can give the leave it command so he does not antagonize the older one.
AT this time you will want to keep them in separate rooms until they are desexed, daily training has begun and is showing success and the learn to earn is in place.
I am going to direct you to a link that goes over the learn to earn. I will also direct you to clicker training as positive training works best.
Once you have put all of the above into place you may need to do some behavior adjustment training to bring them back together.
Clicker training/positive method training/ print off
video’s to see how clicker training is done, scroll down to videos http://www.clickertrainusa.com/clicker-training-videos.htm
clicker maintaining focus http://www.clickertraining.com/files/auto-eye-contact.pdf
Dr sophia yin learn to earn https://drsophiayin.com/blog/entry/the-learn-to-earn-program/
Training method BAT http://empoweredanimals.com/