Cat behaviour during illness

My 16 year old Tom is very ill, though he is just acting old at the moment, but what puzzles me is how the female whose 14 is acting, she is sleeping by Toms side when he goes to sleep, something she never has done, does that mean I am losing him soon, or does that mean she knows his ill.

It could be either.
   
She is obviously sensing that he is ailing and is hanging out with him, but it doesn't necessarily mean that his death is imminent.
   
We had two cats who didn't get along. When we had the female spayed and she came home, the male, who was there first and despised her, sat down next to her. He did that until she was her old self again, when they went back to ignoring each other.
   
Obviously being spayed was not life-threatening but the other cat knew she was under the weather and was attentive.
   

That makes a lot of sense, she is now ignoring him since he has perked up a bit, with help from glucose in his water. I feel we have bonus time with thomas.