CAPITAL GAINS TAX
As you may know, from 6 April 2015 non-UK residents who make a gain from the disposal of UK residential property will be liable for Capital Gains Tax in the UK. Take a look here
for information on that.
The gain from the sale of a property is treated as having accrued evenly over the entire period of ownership. The first £11,100 of gains made in a tax year by any individual are tax free. The balance of the gain will be taxed at 18% or 28% or a combination of the two rates depending on the level of income in the tax year of disposal of the property. Look here
for information on how to work out your CGT rate. As your brother is non-UK resident, only his UK income will be used to determine his CGT rate.
If the property is the main residence of the owner or a part owner, then their share of the gain can be exempted under the main residence rules which.
INCOME TAX ON RENTAL INCOME
You will each need to register for self-assessment to disclose the rental income annually after the end of the tax year on 5 April. As your brother is non-UK resident, he will need to register with HMRC under the non-resident landlord scheme which you can read about here
You will be entitled to a personal allowance as you are UK resident which you may already be using against other sources of UK income. Your non-UK resident brother won't be entitled to a UK personal allowance as you will see here
Income Tax is charged at 20% on the first £31,785 of taxable income, at 40% on the next £118,215 and at 45% on income in excess of £150,000. Any tax due for 2015/16 will be payable on 31 January 2017. You may have to make payments on account as you can read here
.TRANSFER TO SINGAPORE
The solicitor who handles the legal work when selling the property will arrange a transfer of funds to your brother's bank in Singapore.
I hope this helps but let me know if you have any further questions.