I am not an expert in estate returns. This one to me seems a tad tricky to me when it comes to the correct #'s to use because of multiple owners and dates.

The simplest way i can explain is a Father died in 1997. Left behind a house to one of his 3 sons. Shortly after the death of the father the one whom the house was left to added his two brothers to the deed. One of the 2 brothers added to deed after death of the father has lived in the property as his primary since 1998 up until his passing in April 2022. There was no will for the deceased brother that passed in 2022. The Original son that was left the house went to probate court and became the fiduciary of the deceased brother’s estate which included his share of the home.

My question is. Upon death of the brother in 2022 the home was deeded to son 1 son 2 and son 3. The ownership structure was a 1/3rd each. The remaining two brothers/owners of the property sold the home in Dec 2024 after going through proper legal channels. What is the brother that died in 2022 correct cost basis for his estate return?

Do I use the FMV in April 2022 (as my cost basis on the 1041 for the deceased brother) plus any capital improvements and selling expenses? Or does the basis somehow get stepped up to 2024 numbers.
Im confusing myself since there are a few people involved and multiple dates to consider.
Please let me know if you need any additional info or if i didn't explain enough. And thank you for any help!