Congratulations Abs, J, M & H!
If it means anything to you I was 12 when i got my 1st little sister & 16 when my 2nd baby sister came along, it was insanly crazy & my mum used to make me do ALOT with both of them and I hated it, but knowing you & knowing your an awesome mum your nothing like that & i think M will enjoy ther experience & you will have alot of fun & Im sure M will be a great help shes a good kid!