In Act I Scene III Ophelia, Laertes, and Polonius are together. Laertes is getting ready to sail and Ophelia and Polonius are there to say good-bye. In lines 481-535 Laertes is warning Ophelia about being very careful of Hamlet's advances. Laertes tells her that Hamlet might be very sincere when he says he loves her, but that Hamlet is not free to select his partner. Hamlet is a Prince and is responsible for the whole country(state) that he will someday rule and the country's citizens (state's people) will choose his partner. Laertes tells Ophelia to believe Hamlet and agree with what he says but to fear him and his intentions.
This is an example of a big brother looking out for the welfare of his little sister. He is trying to protect her from being hurt or ruining her reputation by giving in to the plea's of love from Hamlet.
"His greatness considered, his intentions are not his own,
He himself is subject to his birth as a prince.
He may not, as lower persons do,
Select for himself, for on his choice depends
The safety and health of this whole state,
And therefore must his choice be subject
To the voice and consent of that state
That he is the head of. Then if he says he loves you,
You would be wise to believe it
Because then being in his particular act and place
May do what he says, which is what
The majority of people in of Denmark go along with.
So decide what loss your honor may receive
If you listen to his songs with a too believing ear,
Or lose your heart, or lose your virginity
To his wild sense of bad timing."