If parents have any right to be biased, it should be in favor of girls. Almighty Allah mentioned girls first before mentioning boys while referring to His sovereign control over the universe and creation of human beings in the chapter Al-Shura (Poets).
To God belongs the dominion of the heavens and the earth. He creates what He wills (and plans). He bestows female (offspring) upon whom He wills, and bestows male (offspring) upon whom He wills. Or He bestows both males and females, and He leaves barren whom He wills: for He is full of Knowledge and Power. (Verses 49 & 50)
The Prophet Muhammad (peace be upon him), has clearly demonstrated that a girl is not a matter of humiliation to a family. On the other hand, she is a matter of pride. A man who brings up his daughters in a proper way will be among those who have the honor of standing close to the Prophet (pbuh) on the Day of Judgment.
Anas bin Malik reported Allah's Messenger (may peace be upon him) as saying, He, who brought up two girls properly till they grew up, he and I would come (together) (very closely) on the Day of Resurrection, and he interlaced his fingers (for explaining the point of nearness between him and that person).' (Al-Bukhari)
In spite of such clear texts, a considerable section of Muslims in many parts of the world believe that spending money on the proper upbringing of girls, including educating them, is a waste of money.
It is also unfortunate to note that mothers in many Muslim societies, apart from aborting a female fetus, are reluctant to feed their girls properly. On the contrary, the parents struggle hard to feed their boys. Parents are also not keen to take sick girls to hospitals as they do with their sons. But this kind of discrimination between boys and girls is a gross injustice and a violation of the teachings of Islam.
In an incident narrated by Mother of Believers Ayesha (may Allah be pleased with her) the spiritual benefits of feeding and taking care of girl children are unequivocally clear.
Ayesha reported: A poor woman came to me along with her two daughters. I gave her three dates. She gave a date to each of them and then she took up one date and brought that to her mouth in order to eat that, but her daughters expressed a desire to eat it. She then divided the date that she intended to eat between them. This action of the woman impressed me and I mentioned what she did to Allah's Messenger (peace be upon him). Thereupon he said: Verily Allah has assured Paradise for her, because of (this act) of her, or He has rescued her from hellfire. (Al-Bukhari)
This Hadith shows how important girls are to parents, particularly as a means to escape the hellfire.
The sayings of the Prophet should be the only guideline for any Muslim community in any part of the world. There is no justification for any Muslim community to be influenced by any other cultural sentiments that drive people to neglect and abuse girls.
In fact the model for the relationship between a father and daughter should be the sayings of the Prophet (pbuh).
The Prophet (pbuh) said: Fatima is a part of me, so whoever angers her angers me. (Al-Bukhari & Muslim)
Media reports such as girls being married off and then tortured by their husbands and in-laws at tender age or young girls being discriminated against by parents show a growing tendency of girls' abuse prevalent in some Muslim countries.