In the ending of Men In Black 3, it depicts J's father's death as sort of replacing K's death. (as stated in Griffin's dialogue). But K also kills Borris, who didn't die in the original timeline or the altered one (where Borris kills K). So whose death is Borris replacing? And wouldn't it have been possible to save J's father instead and just have Borris die to cater for K's death?
As J's dad had died in the original timeline, young K's death in the rebooted timeline would have replaced J's dad's(meaning that J's dad was alive in the version of the timeline where Earth was invaded. So, yay?). By this logic, young Boris's death should have replaced both J's dad's and K's deaths. However, because young Boris killed J's dad before K could kill him, this means that someone else's life was spared. This is the only explanation that supports the "where there is death, there will always be death" idea.