When you leave the house, (in the forest) carrying the baby. Go straight down, into the fire.
(To be exact, you're backtracking from where you entered the forest. But you will see a fire blocking your way.)
Bump into this fire again and again, until you cross through it.
And just follow the path, to the 5th False Ending.
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And I'm super happy you're liking the game. And that you find it interesting enough to see all the endings.
Thank you so much, Kahnwald.