Here's why:

* The Milky Way is a galaxy: It's a massive collection of billions of stars, including our own Sun.

* Mars and Venus are planets: They orbit our Sun, which is a star within the Milky Way galaxy.

Think of it this way:

* Our solar system is a tiny speck within the much larger Milky Way galaxy.

* Mars and Venus are part of our solar system, meaning they are within the Milky Way.

Imagine a giant beach with a tiny grain of sand on it. The beach represents the Milky Way, and the grain of sand represents our solar system. Mars and Venus are simply part of that tiny grain of sand.