As mentioned, you cannot combine PNRs. You may split, but once split, they cannot be recombined.

I have booked a paid ticket for myself and award for family. You can call to assign them a MCE seat if you have access by status.

Very useful to know that "To Complete Party" is the magic phrase to link the PNRs. In one case I called once to assign the family MCE, but it was a one-time thing. When I accessed their PNRs, other MCE seats showed as selectable for a fee. But then a schedule change caused automatic rebooking of one segment, and I and the family were rebooked onto different flights. It took a long call to sort that out, but the agent must have done the TCP because she told me that from there on, we'd be more likely rebooked together in case of another schedule change. And IIRC after this, MCE seats were showing as selectable without a fee for my non-status family.