A couple of my Koi got sick recently and one has now died, but I was surprised at the behaviour of the healthy ones. Before it died the fish started to list to one side, the healthy ones were constantly trying to get it stable by pushing it upright. Now I have another one that seems to be sick and the one remaining healthy one never leaves it side. I have had these fish for around 4 years so I guess they have formed some kind of bond.

We are all connected. People are more eager to help family members and loved ones, with whom we have a close bond to, than with a total stranger. Same with animals. Even though they not have the human capacity of intelect, they still have the natural nurturing instinct. Which is automatic.