We were all fetuses once. Every single walking breathing human. And even those that aren't any more. A fetus is as much like me as a newborn, or a toddler, or an adolescent or any other stage of human development. It's a stage we all pass through to get to where we are now.
An egg might not be a butterfly, but once it is fertilized, the larva and pupa stages are as much a butterfly and the winged creature that we see on spring days.