Shakespeare certainly presents a very unstable family relationship in Act 3, Scene 5; however, it is also a family relationship that is very characteristic of the time period.
It is in this scene that we see Juliet's parents very quickly turn on Juliet. In previous scenes, Juliet's parents appeared to care very much for Juliet's well being, especially her father who refuses to grant Paris permission to marry her unless Juliet also approves of the match, showing us that Lord Capulet has his daughter's happiness in mind. Even in this scene, Juliet's mother begins by showing concern for the fact that Juliet is so deeply in grief. Lady Capulet rightly sees that such severe grief is unhealthy, as she shows when she states, "Some grief shows much of love; / But much of grief shows still some want of wit" (III.v.73-74). Therefore, both of Juliet's parents appear to sincerely care about their daughter's happiness, and probably do care; however, as soon as she expresses her own point of view, they turn on her.
Both of Juliet's parents believe that a happy, celebratory wedding will distract Juliet from her grief, which they assume is grief over Tybalt's death. They also both expect complete obedience from their daughter, which was what was expected of children in that time period. Therefore, both are completely shocked when Juliet refuses to marry Paris. However, both of her parents show their true colors, and just how unstable the family relationship is, when they give their harsh reactions. For one thing, it was silly of them to suppose that marrying a man she has never met would help her out of her grieving state. Therefore, their harsh reactions are very character revealing. For example, Lady Capulet gives a very harsh reaction when she says she wishes Juliet were dead for having refused Paris, as we see in her lines, "Ay sir; but she will none, she gives you thanks. / I would the fool were married to her grave!" (142-143). Even Lord Capulet gives a very harsh reaction when he threatens to disown her should she continue to refuse, as we see in his lines:
An you be mine, I'll give you to my friend;
An you be not, hang, beg, starve, die in the streets,
For, by my soul, I'll ne'er acknowledge thee,
Nor what is mine shall never do thee good. (200-03)
In other words, in these lines, he is saying that if she does not marry his friend Paris, then he will disinherit her. This reaction is especially shocking considering how concerned he was for her happiness in earlier scenes, showing just how unstable his character and their relationship is.