Published: Oct 09, 2010 8:31 PM EDT
Updated: Oct 09, 2010 5:31 PM EDT

CAPE CANAVERAL, Fla. (AP) - The stars may have finally aligned for the world's only space sibling team.
Astronaut Scott Kelly is circling the planet, headed toward a Saturday night linkup with the International Space Station. His identical twin, Mark, will join him next year, if NASA's shuttle schedule holds up.
Together, they will become the first blood relatives to meet up in space.
Scott is the space station's next commander. He took off aboard a Russian Soyuz rocket early Friday. Mark is space shuttle Endeavour's next commander. He's due to take off at the end of February. It's currently slated to be NASA's last shuttle flight.
The brothers plan a little arm-wrestling when they unite in orbit. Each is predicting victory.