Although they share the same airline alliance, they are two different airlines, with two different frequent flyer programs. So No. But, depending on your end goal, you may be able to redeem from each account and fly on one of those airlines.
For example:
Redeem 25,000 CO miles for a United flight
Redeem 25,000 UA miles for a United flight
2 people can fly together on the same airline, within the same alliance.