Agree with above posters. SSWU/SWU/NAU upgrades are all restricted to the respective fare classes noted on their certs. Just like not being able to u/g on a Tango fare, you cannot upgrade reward travel.

This isn't a change in policy - its the way its been certainly since I became an Elite flier for the first time in the late 90's.

A much better solution would be to book your spouse/child in biz class using Instant KK and then play AeroLotto with your upgrade.