Should we call for a welfare check for a family member who seems to be declining?

Six years ago my mother-in-law passed away. She left behind her longtime, live-in partner and her only son-my husband. While the partner is not a blood or legal relation we have still considered him family and stayed in contact with him. He is 79 and has diabetes. He does not share much with us, and only gives us general info when we press the issue. He looks unkempt/unbathed, clothes needing to be washed, hair dirty and in disarray. He is still driving although we do not feel he should be. We have not been inside his house in years, only to the front door, but from there we can smell animal urine (my mil was an animal lover and had many cats and dogs) and probably just general filth. He is a very stubborn man, and will not admit he needs help, let alone seek it out. He does have a son and daughter both out of state, but they are either not in contact or don't seem to care. Should I get in touch with somebody to do a welfare check? If so, who would that be? Any advice is appreciated on what the best course of action would be.