The Penetration fortnite has had across ages 10-20 is almost surreal. Anecdote: I was playing Apex (and Siege, for balance...) and I can hear my friends younger brother playing fortnite with his friends - across the room -through the chat.
My 14 year old cousin visited this week and has already shifted to Apex Legends... After months of being invested in fortnite.
Loyalty in non-rpg fps games is fickle.
No game may shine the way fortnite is in its peak for a while, but I do not see it having the longevity that the industry believe it will have.
This also helps explains why you're younger brother was still playing Fortnite and why it's not gonna die to Apex.