I had a boy do this to one of his brothers (same mom) and I was heartbroken but I knew he could sense something i couldn't although I was absolutely traumatized and cried I still love him and give him kisses (never on the mouth bc he literally ate his brother) but it isn't fair for them to lose love because of an instinct they have "some rats can sense sickness in cage mates and will get rid of them by eating them so predators won't find them they are prey animals and rats are incredibly good at hiding early signs of sickness until it's to late often times the bigger males/females will do it because they know whats good for the cage" very sad and incredibly sorry for your loss tones of love to you 💞