There is no good way to do what you want. There is no way that you can split the IRA with your siblings. There is no way that it can become an IRA for them. All you can do is take money out, pay the tax on it, and give money to your siblings as gifts. A gift is not taxable income to the person who receives the gift.
Any money that you take out of the inherited IRA will be taxable income to you (but will not be subject to the 10% penalty even if you are under 59½). You will get a Form 1099-R at the end of each year showing the amount that you took out of the IRA. You have to enter the 1099-R in your tax return. There is no way to transfer the tax obligation to your siblings. You cannot issue 1099s to them.
As Opus 17 said, if you give any one sibling more than $17,000 in any year, you must file a Form 709 gift tax return. That is not part of your income tax return, and you cannot file a gift tax return with TurboTax. The $17,000 limit might be increased in future years to adjust for inflation.
