My Sim's grandmother, who lived outside the household, passed away due to old age. When she died, I got the First Loss milestone. I scheduled a funeral for later in the day and had my Sim and his entire household attend. Earned a Gold on the Funeral event itself but when they returned back home, the milestone for First Funeral did not complete. No mods or cc.
Edit By Crinrict: Added missing pack tag to title.