One more thing, @demitx475:
Unless your mother actually sold assets to this irrevocable trust, then the transfer is likely to be considered as a gift to the beneficiaries. As a result, a gift tax return (Form 709) might need to be filed.
See https://www.irs.gov/instructions/i709#en_US_2022_publink16784xd0e314 ($17,000 per donee for the 2023 tax year).
If the value of the assets transferred are substantial, you should consult local tax counsel.
