If he has a separate marketplace insurance plan then he needs to file a separate tax return and if you claim him as a dependent he may need to repay all of the subsidies he took.
If he is on your marketplace insurance plan then you can claim him or not claim him as you see fit. If you choose not to claim him then you will divide the amounts on the 1095-A by however many family members there are and put his share on his tax return and the rest on your tax return.
@Stacyndanny
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