How do I calculate my cost basis for a property that I was listed as a joint owner on with my brother? He passed away, and I sold the property.

My brother added me as a joint owner on his home in 2002. He passed away in late 2021, and I sold the property to a family member in early 2022. How do I calculate my cost basis since I technically only inherited his half of the property considering I was listed as joint owner prior to him passing?