I want to send USD 22000 to my brother's NRE account in India. I pay taxes in the US. Are there any other tax implications for this transaction in US? Also, this money is not a gift. My brother will repay the amount (principal only)
Your brother is also an NRI and hence eligible to hold an NRE account? What country is he residing in?
Unless you have proper documentation to establish that this is a loan, it is considered to be a gift by the IRS, and you are liable for gift tax on $8K (= $22K - $14K annual per-recipient exemption) in the US when you send your brother the money. On the Form 709 that you must file in the US (it is not attached to your Form 1040 but is instead sent to a different IRS office), you can choose to reduce your lifetime combined gift and estate tax exemption (currently $5.4M but wait till the Trump Tax Act becomes law when it will likely be even higher) and not have to pay any gift tax at all. (Or you can pay the gift tax and be done with it.) If you are worried about reducing your exemption below $5.4M, congratulations on your achievement of (or aspiration to) a very large net worth so early in life, and talk to your lawyers about alternative strategies. As far as your brother is concerned, he does not have to pay any taxes (income or gift) in India when he receives the money or when he returns the money since gifts of money between close relatives are not taxable in India.
The loan must charge a minimum interest rate as specified by US law, and if you choose to forego this interest (since you say that your brother will be returning only the principal to you), then you are making a gift of the annual interest due (but not collected) to your brother. On a $22K loan, the annual interest will be less that $14K and so this annual gift will not be liable for gift tax. In the best of all worlds, your brother will send you the interest and you will return it so that there is a paper trail showing interest paid, and a small gift given (cf. the answers and comments on this question.) Finally, since you bring up 2017-2018 in your comment, be aware that the US tax year runs from January 1 to December 31 for most ordinary taxpayers, and so at least as far as the US is concerned, the lending and the repayment are likely to be in different tax years even though they might be in the same tax year in Indian law where the tax year covers parts of two consecutive calendar years.