Boaz purchases Ruth as a wife (Ruth, Chapter 4) - I remember when I first got married, and my wife's father gave her to me.  Though the ritual is largely symbolic these days, we shouldn't remember the tradition from which it came.  In the past, wives truly were the property of the husband.

Ruth, the Moabitess, was a widow.  However, and if I'm wrong someone please correct me, it seems she was still technically the property of her dead husband.  But, since he was dead Ruth was under the care of her dead husband's mother (Naomi).  In order for Boaz to marry her, because he did love her, he basically had to purchase her from Naomi, and to sweeten the deal he purchased Naomi's crops and basically all the belongings of both Naomi and Ruth's dead husbands (who were the true owners).

What happens next is utterly ridiculous.  Ruth and Boaz get married, and they have a son named Obed, who will later be the father of King David.  Naomi, who is too old to conceive, assists in the raising of her "grandson" by nursing him.  Naomi's not really a grandmother, of course.  Because Ruth got married to a new man, Naomi has no claim to the child.

She's just an old friend - a really old friend who happens to be able to produce milk at an advanced age!