Fee/commission override

I've actually been an advisor for a few years and I share an office with a senior advisor. To make a long story short there is a 25% over ride on my commissions (I have a S7&66) only since the other advisor does not have a S65/66. I'm curious how common this is in the industry and what is considered a typical override. I feel stuck since a chunk of my paycheck goes to the other advisor. We do not share a book of business and yes the other advisor helped me get started but I feel like I'm just viewed as easy money. I have approached this individual and wanted to renegotiate things but there hasn't been any budging on it. My GDC has increased between 15-20% each year and I could help split office expenses. Any advice or guidance would be greatly appreciated.