The main problem you would have is that Membership Rewards and Ultimate Rewards have nearly completely different partners. Your best best for MR is probably Delta as others have mentioned. But UR is probably going to be United or BA (Korean is also a Skyteam UR partner, but their redemption is quite complicated). So the two of you might end up on different airlines if you tried to split your points that way.
One option might be to get two one-way awards through UR and then two one-way return awards through MR for example. United would probably have pretty decent options to FCO in business and they don't have a lot of fuel surcharges (that's where BA tends to get you).
Unfortunately, Delta doesn't really allow one-way awards so you're a bit out of luck there. You might want to look at other MR partners for the return. For example, if you could find a cheap ticket from KBP to LHR, you could fly Virgin Atlantic back to SFO which is great.