Genuinely curious as everyone with younger siblings I've spoken to seems to agree with this...
I'm 26, have a DB of 18 and DS of 16. My mum had me when she was 20, met my DF (step) when I was three and then went on to have my brother and sister.
When I was growing up, I was never given pocket money and was expected to get the bus anywhere I wanted to go. This included two buses each way to and from school. I had to get a job at 16 to afford to eat at college and have some spends on XYZ. I had to pay for my own phone and contact, I was never allowed friends over etc.
As my parents have gotten older, they have gone completely soft and my DB and DS want for nothing. They have phones paid for them, get lifts wherever they want to go and get £20 pocket money each a week! My mum is still driving my DS to college despite having a free bus pass and buses being every 15 mins! She is definitely the most favoured out of us!
It's defenitely not a money thing as they are worse off now than what they have ever been financially.
My DP's mother is the same with her DD who is the youngest of DP's siblings.
Have you noticed that your parents treat the youngest any different to how they treated you? Or if you're a parent, why do you go soft?