TurboTax does only let you put in one social security number for a person who is on your your marketplace plan, but not on your tax return.
You can divide the percentages any way that all of you agree on. If you take 50% and one son takes 50%, then the remining two people would use 0% on their returns. The only stipulation that the IRS has is that all parties agree to the way the percentage is divided and that the amounts taken add up to 100%.
You will use the social security number of one of your son's on your return. The son's will use your social security number as the person that they share the 1095-A with. They will each use the agreed upon percentage on their returns.
