Hi Expecting,
CONGRATULATIONS on expecting twinnies! They are just the best!
I did it the other way around to you. I had twin girls and when they were two (just) I brought my little singleton home.
I put them both into pre school 1 day a week and I did it about a month after Lily came home. They were just fine. It was difficult at times but I did things like buying a baby doll for each of them to 'breastfeed' everytime I sat down to feed Lily. They also got to know and Love the Wiggles then! They were my babysitters when I needed to settle Lil.
It will be tough at first but so is bringing home just one baby into a house. Everything changes but with time your little ones will grow up to be good friends. For ages Lily used to call herself the third twin! Poo to anyone who says you can't do it! Women are AMAZING! We can do anything!!!!
PS I brought my second set of twins home in January this year and that was different again!