Well, there's no changing it lol. Get ready for screaming. At least you'll be out in 2 years.

I should have worn a condom.

Also, just punch her in the stomach if you really MUST do something about it.

Otherwise, suck it up until you're 18.

Sorry but thats the way the cookie crumbles.

And with 3 babies on the way, you're gonna see lots of cookies crumble.

Haha :')
I'm 16 and only have an older sister, I'd LOVE to be in your position right now haha
Just don't think negative, at the end of the day they aren't just any random children haha they're YOUR brothers or sisters and you'll love them - they may not even be annoying haha :')!
Just don't be cynical haha, and yeah .. get ready to have attention took away from you for a while, and get ready to help out tons!

Congrats to your Mum though!