How can one act when his parents refuse to complete his marriage to a committed and ideal girl whom he loves and considers suitable for him, despite their approval of the girl herself, due to their objection to her family after they had previously agreed to the engagement, knowing that he is a dutiful son to his parents?

If the girl is religious and of good character, you should not be hasty in abandoning the engagement. Try to convince your parents with the help of righteous people, and remind them that Islamic law considers compatibility (kafa'a) to be from the man's side, not the woman's. The author of Bada'i al-Sana'i said: "Compatibility is considered for women, not for men." Ibn Qudamah said: "Compatibility is considered from the man, not the woman." If your parents agree, then praise Allah. Otherwise, it is not permissible for you to proceed with this marriage, as it involves disobedience (to parents). And perhaps there is good in that. It is also not permissible to establish love relationships between men and women, even for the purpose of getting acquainted before marriage.