I have 4 year old twin boys. I don't have any other kids, but I can tell you that I needed a lot of help at least the first 6-8 months, especially for overnight feedings. My advice would be to start planning on who can help you during this time, friends or family :-)
Lol ! You Are Definitely Gonna Have Your Hands Filled....
Pray For Patience! Me And My Husband Have His 5 Brothers , 17,16,11, Twin 6yr Old Boys , My 2 Yr Old Daughter And Expecting Another... Everyone Says Were Having Twins But OMG , I'm Already Going Insane With All The Others. Its Extremely Hard , I Wish You Luck. The First 4mnths Are The Hardest After That Its Still Hard But Not As Bad Lol