In the beginning, I allocated 100% to the parent. Then the son received IRS letter requesting him to file Form 8962 to report his share of the policy. The son does agree to report his share of 33% to resolve the issue.
His parent's return tax amount does not change much due to income, but they agree to split the policy.
Do you know if the IRS has record of split percentage of participants listed on Form 1095-A? Or does the policy specify the percentage of each participant?