Explain why you think the topic of parent/child relationship is as relevant to modern audience as a seventeeth century audience.
I guess I would turn this question around -- why wouldn't it be as important or relevant? I cannot imagine a time when parent-child relationships will not be relevant.
I think that the relationships between parents and their children will be relevant to people as long as we (mostly) live in nuclear families where the parents are making rules for their children and the children are growing up.
My kids are 5 and 8 right now, but I already spend a lot of time thinking about how to raise them the right way and how I will try to deal with them when they are more like the age of Romeo and Juliet in this play.
Because we parents are responsible for our kids' growth, and because you teens want more independence and less interference from parents who feel responsible, the relationship between parents and kids remains relevant to audiences today.