Inheritance in a relationship

Hi! So, I am about to inherit a good sum of money, and am deciding what to do with it.

Me and my partner bought a house 50/50, we earn around the same, put in the same deposits and split everything 50/50 too.

One option is to use some of the inheritance to pay off some of our mortgage. If I do this, our monthly payments would be lower and I’d still expect these to be paid 50/50. However, I would also want the split in our house to be revised so that if anything were to happen, if we sold I would get back the extra money I put in.

While wanting to share the money I inherit to a degree, and use some to allow us to treat ourselves, I see it as my inheritance & would like to be able to use it as such. My partner disagrees, saying it should be our money and if the roles were reversed he’d see it as our inheritance not his. We’re not married and have no kids.

Am I being unreasonable? I’m just trying to be financially responsible & have quite a practical approach to things.