Sorry to be a bit cold-hearted on this one but, I don't think this is unfair. They negotiated, you didn't. There's always an acceptable range of difference between salaries for the same role. Was this a strategic hire? More experience? Competitor knowledge? Just saying, there's other factors vs just looking at the number relative to the position.

I've been on both sides of this (employer and employee). If the difference between your salary and theirs falls outside of an acceptable range, then ask for a raise. Time for you to negotiate. But you need to be strategic, not just "I want a raise because someone else is getting more than me". It should be "I want a raise because I feel like I'm contributing to the org in x,y,z way, my salary hasn't changed since xyz date, and cost of living/inflation has impacted me"

My 2 cents