This one is going to be tricky - I agree with others that you’ll want to start with whether there are disability aids he qualifies for. Definitely don’t word it as “foreign” as it isn’t that (unless it is, then that’s a different issue and one I won’t touch).
I know I’m a Yankee and married a Southerner. Both of us have modified our speech quite a bit, but I still need to “translate” for him in many places up north - esp for things like, “Do you want rice or fries?” as many people can’t understand the difference as he speaks it and it definitely makes a difference. For the “other” direction, his dad really has never been able to accurately understand me. Even within our marriage H has to let me know if he means a pin or pen - I swear - those words sound the exact same to me the way he verbalizes them. We have cute family memories how one of our lads grew up with a speech problem, being unable to articulate half the alphabet. Down south no one had any problem understanding him. Up north no one could understand him by words alone. Such is life.