Let's say this set of parents have 3 adult kids. Two have good jobs and earn about twice as much as the youngest. This isn't a privilege, it was earned with hard work on their part and careful career projection.
The youngest has always been more distant from them, more self-centered and hedonistic, less career-oriented. She has had several average and below-average jobs. As for savings, she never had more than two monthly salaries' worth in her account (in her own words). This she blames on the job market, of course, however she doesn't hesitate to travel constantly, buy tickets for expensive events, go to restaurants regularly, and so on. She consistently complains to her parents about her job situation and how it's "impossible to sabe money".
One of the older siblings managed to save enough to buy a car and buy a house even though her income was as low as her sister's for a long time. She saved, improved her skills and changed jobs until reaching her more favourable current situation. The parents did not contribute financially more than a present here and there.
However, once this older sibling bought a car, the youngest got a car from her parents for free. Once she got an apartment, the parents started PRESSURING the youngest to buy one until she gave in, and they literally payed for half of it. They surprisingly admitted that they would have gladly paid for all of it ("whatever suits you best"), but she refused—I'm assuming because she was worried that she'd be perceived as a leech by the rest of the family or because she suspects this "present" is not for free as the parents expect affection/ attention in exchange.
This has bred resentment and disbelief in the older siblings and has had a negative impact on family relationships. The parents seem to feel a special compassion for their youngest and are always very anxious to help her. Also this seems to be the way the parents "buy" a place in her life. The oldest kids are normally more family-oriented and they visit regularly, so they feel taken for granted. Also the mother is way more physically affectionate towards the youngest. Simply put, she's the baby of the family and must be taken care of, poor baby.
Are the older siblings unreasonable for thinking this is unfair, despite the fact that they are better off financially than the youngest child?
P.S. If you think IABU indeed, please be kind enough to reflect in your answer if you favoured one of your own children over another and why. Thanks!