You may have hit upon something
He IS losing his sight. He has cataracts on both eyes, and I believe he may be hard of hearing (the reason for his loud barking). But I've noticed this bad behavior for quite some time, even before they came to live with us. My wife feels like she is caught in the middle. She feels it's between her folks and I (it puts me in an uncomfortable situation) The dog has also snapped and growled at her (but hasn't bitten her yet) ;)
That will be the next step
First I'm going to try a permenent drag leash when he is around just the immediate family. When the grand kids visit, I will insist he be kept in the in-laws' quarters. Thanks for the suggestion.
He's always been badly behaved
Way before the other dog's death. I remember him facing off against my sister-in-law five years ago in her home. The dog has recently been checked by a vet (of course, his behavior wasn't mentioned).
The situation escalated this morning. My wife has thus far refused to get involved, so I was forced to approach her parents. I did so in a non-accusatory manner, suggesting the drag leash. They became very defensive, basically accusing me of making a big deal out of nothing. They attributed the dog's behavior to old age. When I pointed out that he has been this way ever since I can remember, they claimed his snarling and biting is perfectly normal, even after showing them my finger (which is still bruised). The other evening, after I was bitten, my in-laws saw me apply an ice pack to my swollen finger, yet neither inquired about my injury. Meanwhile, my mother-in-law talked soothingly to the dog and stroked him. I know this sounds almost comical, but I'm at odds as to how to proceed.