I'm slowly working my way through ticking off all of the Total War Rome 2 Emperor Edition achievements but I cannot get the Et tu...? one to work.

The achievement asks that you assassinate a member of your family which i understand you do via the family dynasty screen, I've done it in 4 different campaign games now but still don't have the achievement.

I've found guides online that say you need to go to patch 16 but that isn't an option anymore and I've seen other guides online about saving at specific times and reloading at specific times but this hasn't worked for me either.