I was really confused for a second there. But let me get this straight...
Baghead-kun's (I forgot the MC's name lmao) father was one of the first to be affected by the game and went through a very similar experience as Baghead-kun-- having his memories erased and eventually suffering from delusions that turned him into a serial killer, killing Minamiko's parents.
Later on Baghead-kun played the same game, got the same delusions after having his memories wiped, and went to kill Minamiko's aunt, uncle, and cousin. For a bit there I thought that the family that Baghead-kun was about to kill was Minamiko's mom and dad from the past.
But that doesn't make any sense lmao so no, it's the aunt, uncle, and cousin that we saw for one panel 200 chapters ago. I think...?