It's not necessarily a bad thing. Marriages that are arranged that young are not consummated. In a sense the husband takes on a kind of parental role until the girl is older.
From everything that I have heard, arranged marriages work out just as well, or perhaps better than, marriages in which the man and woman choose each other.
There's a tradition in early Judaism and Christianity that although the parents arranged the marriage, the bride or groom could say "no." The marriage of Rachel to Isaac is typical. The whole thing is arranged and she does not see her husband, but she is given a chance to consent.
Marrying one's daughter-in-law is typical? I think you've got them mixed up.
Isaac's wife was Rebekah. They had a son named Jacob, who later married Rachel and her sister Leah; he also had children by two of their handmaidens.
Rachel and Leah were also Jacob's cousins. I believe their father, Laban, was Rebekah's brother.
Aren't you glad we don't follow Biblical customs anymore?