Children raised in space should be able to return to Earth as long as a rigid exercise program is developed.  Because we normally live under the pull of gravity, our legs are important appendages, supporting our body weight, and our heart is an important organ, pumping blood up through the body.  In the weightlessness of space, however, the muscles and bones of our legs and our heart muscles weaken, so astronauts must do a lot of special physical exercises to keep them strong.

Now if a baby were born in space, I'm not sure what kind of exercise could be devised to ensure that its heart and legs grew strong enough to endure Earth's gravity.  That is a more difficult proposition.

NASA has some information on 'Living in Space'; I have provided their URL below.