Do other cats know a cat is dying?

Our oldest Molly is pretty sick. Doc has not said she's terminal but
she's 14 plus and when you considered the big picture I am not
hopeful.

For her own benefit, and hygiene's sake, we've had her quarantined
most of the day. She's out when we are home and when we can keep an
eye on her.

Our middle boy, a super sweet and sensitive main coon, is also off his
food and making uncommonly pathetic noises for him, distressed
sounds, a major case of the shivers earlier today and being extra
needy. (some of this is due to the new cat, but the noises are new.)

our #3, the newest cat, has only been here 8 weeks and seems fine, how
ever we are not 100% certain what norm is for her so she could be off/
upset and we don't know it.

so is #2 just upset about molly being so sick or does he know
something we don't?

CS