Question about family transfer / securing a firearm

My FIL is getting to the point with his health (**NOT mental - more referring to a blood sugar or other incident**) where I am worried that it may not be advisable for him to keep his shotgun lying around. I'm going to be moving closer to him shortly, and filing for a FOID in the event that I need to transfer the gun to my ownership ("keeping it safe" for him ... he bought it several years ago out of nostalgia and has never actually gone hunting in ages). I'm not even sure his FOID is active anymore.

I understand that the state wants you to have a FOID and legally transfer the gun over, but what's the best way to handle it if things get to a point where I feel that it becomes necessary to take ownership of the gun to ensure it remains safe before I get the offically issued FOID?

Note: I'm well aware of all the politics and associated feelings surrounding gun ownership laws & FOID. I'd prefer those comments were left to yourself. I'm only interested in facts and the best way to handle things here as the laws currently exist.