Oh, they look like they're only a couple of days old!!! Will you try to find the mommy cat at the empty house?

Here's a link that may give you some good information on hand raising kittens: http://www.hdw-inc.com/tinykitten.htm

It's wonderful that you can take them with you while you're at work!

And yes, you have to give them belly rubs after they have eaten, otherwise they cannot poop and pee.

As far as I know, you also have to keep them warm since a kitten that young isn't able to hold its own body temperature.

Kirsten