Claribel was sent to be married to the King of Tunsia by her father's orders. It was seen as a way to expand their family's reach to Africa. This would be good for their family. Even though the Africans were seen as a people of "wild" background, completely unrefined comparitvely to how Claribel lived in Europe. Daughter of a King she would of course be well read and educated to a level above her subjects in Africa. Because Claribel weds the King of Tunis, her father will now be able to benefit from the union as well.
When Miranda sees Ferdinand she is in love with him nearly immediately. Her father begs of her to please understand that the world is not merely made up of monstrous beings like Caliban and the attractive Ferdinand. Prospero watches over his daughter Miranda when she is in contact with Ferdinand most likely because he wants her wed to someone with promise. Ferdinand is the furture King of Naples and therefore a perfect mate for his only child. However he cannot help but ensure his daughter's virtues remain in tact, by saying:
"Then, as my gift and thine own acquisitionWorthily purchased take my daughter: butIf thou dost break her virgin-knot beforeAll sanctimonious ceremonies mayWith full and holy rite be minister'd,No sweet aspersion shall the heavens let fallTo make this contract grow: but barren hate,Sour-eyed disdain and discord shall bestrewThe union of your bed with weeds so loathlyThat you shall hate it both: therefore take heed,As Hymen's lamps shall light you." (4.i.14-24)