Since the age gap is quite close, i suppose there will be times the toddler & baby will get jealous over the newborn. Perhaps the 11th month baby will be more jealous. I have a friend who tries this method to minimise the jealousy. Both parents take turns to look after the kids. Eg: Mon,Wed, Fri mummy looks after the infant, Tue & thurs daddy will look after the infant. Weekend spend time together.
You have to try to spend equal time & attention to the older kids so they do not feel unwanted.
In another friend's case, the elder daughter who is 2 years old beats and scratchs the newborn cause mummy spends all her time with the newborn and daddy is busy at work.
If it happens explain to your children that it is not right, do not beat or scold them it will somehow cause them to dislike the newborn even further.