Using ProSeries Basic here is the scenario

Mom and her kids live under same roof as mom's parent. (1 address = all 5 people)

Grandparents of kids and parent of  Divorced Mom with 2 kids in the house

Mom of 2 kids has no income for 2019

Kids receive in 2019 50% of deceased father's pension plan = use 108K each gross, with 20% mandatory w/h fed tax - code 4 on the 1099-R for each.  Also each kid gets SSA Money from deceased father for say 5K each with no fed withholding.  Father died 2018. Mom was divorced at the time and he made the kids beneficiary even though they were minors at 50% each.

Kids birthdays are 11/01/2002 (17) and 3/1/2001 (18) at end of tax year 2019.

Kids have no earned income.  Mom has no earned income. Grandparents are supporting all 3: mom and 2 kids and themselves.  Filed Grandparents return just on the 2 grandparents alone in 2019 as normal with no dependent grand kids this time.

Form 8615 gets massively complicated due to the kids age of 17 and 18 and as well as the parent (mom) had no reportable income.

Had the parent called me to let me know she was going to take disbursement I would have recommended a trustee to trustee Inherited IRA for each child with a legal trustee appointed by the probate court to care for the funds until their age 21 in the state they live in but that did not happen and cannot be undone now.  Disbursement happened in early 2019 prior to this getting into probate.  

Has anyone run across this scenario?  I need to file for these kids and I just got the tax info last week.

Thanks in advance for any input on this crazy case as the TCJA seems to also have some bearing here.

JSH