Huh?

I'm not an animation expert, but my understanding is that visibility is not animatable, nor is the parent of an object animatable.

Only continuously variable numeric quantities (real numbers) can be animated, such as position, rotation, etc.

You cannot animate a checkbox, and even if you could there are no in-between states.

The only way to make something "fade" from view is to go into the materals (all of them) for the object and make the "Transparency" of the material animated from 0 to 1 or vice versa. You can key-frame it so it happens instantly or gradually.

However, be aware that Transparency is not coded to completely make the material produce no output in the render. Certain effects, particularly specular lighting effects, must be also turned off for an object to be fully invisible via shaders. This is because the people who wrote the rendering engine were confused about whether transparency is supposed to be used to define non-existence, versus a material that exists, but lets light pass through, like clear plastic.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)