Whether siblings are 14 months apart or they are twins, they will have their own personality. They are each unique individuals. Expecting them to be the same is neither realistic nor fair. Reward or discipline each according to their behavior.

A word of caution is in order here. Children try to please their parents. They get a read on your thoughts and feelings (oftentimes before you are even aware) and act accordingly. If you tend to see the oldest child as the role model, she (I will assume you have a girl) will attempt to act as a role model. She may even feel that she can never really live up to those standards and thus have low self-esteem. Likewise, if you see your seven year old as a trouble maker, she will take on that role. She may feel the good child role is taken and thus be the bad child. She may feel unloved and thus be rebellious. She may sense that she will always be in trouble, so why try to be good. She can handle the scoldings and will do as she pleases. (NOTE: these are just examples, best guesses, etc.)

I would suggest praising the young girl for anything she does right. Thus showing her she can be good. As to the eldest child, when she/he makes a mistake let him/her know that mistakes are okay. That is how we learn. Maybe give some examples of mistakes you have made and learned from the experience.

Hope this helps.