When Karthus and Kog'maw die at the same time, does Kog'maw's Deathknell trigger twice due to Karthus's passive ability?

Ruling: Yes, when Karthus and Kog'maw die at the same time, Kog'maw's Deathknell triggers twice. Karthus's ability is a passive (not a triggered ability), so it applies even when Karthus dies simultaneously with other units.

Nuances:

• This differs from Viktor Leader's triggered ability, which cannot trigger when Viktor dies at the same time as another unit (due to the rule that a game object cannot evaluate its trigger condition if it leaves the zone at the same time the trigger is satisfied)
• Karthus works because it's a passive ability that "occurs" rather than a triggered ability with a trigger condition