Trust and interest reporting

Hi

I am trying to figure out the best way to report interest between my deceased sibling and his trust ( He passed away in 2024) . I received a 1099 from his bank reporting the combined total of the interest he personally earned while he was alive as well as the interest the trust earned after he passed on one 1099 all in the name of the trust.  I called them and they won't change it on the basis " this is just how they do it"- even if it is not accurate.

Shouldn't the prorated  portion of the interest that was earned by him while he was alive be reported on his personal and final tax return ---with the remainder that was earned under the trust be reported under the trust? 

Any help you can offer will be greatly appreciated.

Thank You!