James
"Fuck you James! You forgot a condom! You're such an idiot!"

During their 6th year at Hogwarts, James got Lily pregnant because he forgot protection.

Lily took a test and told James.

Sirius
"Um, Sirius?" It was a random Ravenclaw girl Sirius had a one night stand with.

He didn't even know her name.

"What is it....... Jem?"

Was that her name?

"I'm pregnant...... and it's yours."

Sirius fainted.

Remus
Remus glared at Sirius and James.

He thought he was just putting on some weight.

But turns out two buffoons accidentally put a potion to make him pregnant.

Let's just say 1000000 chocolate frogs later, he forgave them.

No Peter because let's be honest. Nobody wants HIM to be their parent.