Is it unfair that my boyfriend's dad treats him this way?

My boyfriend is 1 of 7 children. His mother died shortly after birthing him. He is a triplet (with a brother and a sister). His other siblings are all men. They are the youngest. I've noticed the dad treats the girl a lot differently than his sons. For example, for their 16th birthday, he bought the daughter a car and then he bought another car for the two boys to share. Why should she get her own car if they have to share? Their 18th birthday is coming up and the dad is paying for a birthday party for the girl. He buys her everything and just spoils her. I think it's annoying. He obviously favors her over the boys. Don't you think that's unfair?