Kenneth Whiteside, a 59-year-old from Glenrothes, Fife, who lived in Johannesburg with his wife and two daughters, was a planning manager at the In Amenas desert complex.
Bob Whiteside, who lives in Crieff, Perthshire, told how he had learnt of his brother's death at the hands of Islamist terrorists from social networking site Facebook.
He told BBC Radio: "We know now what's happened to Kenny but we actually had to find out for ourselves.
"We were not given any official information and it was through Facebook, of all things, that we found out of Kenny's demise.
"It was my daughter who found it on Facebook, a message from an Algerian co-worker.
"The police came last night and informed us that what was on Facebook was true, that Kenny had been... he was executed."
Asked how he felt the situation had been handled in Algeria, Mr Whiteside said: "It's just the way life is, I'm afraid.
"I don't hold any grudges against the Algerian army or anything because that's the way they work, that's their system and they weren't bothered about the hostages as such, they just wanted to get the camp cleared of all the terrorists. That was their main objective as far as I can see."
Mr Whiteside said his brother was a planning manager and had worked in Algeria for about five years.
Asked if more could have been done to keep the site secure, he said: "I honestly don't think you could do anything, not any more than was done already.
"They had security guards but you can't guard every installation all over the world just because of these fanatics.
If they are going to attack, they'll do it."
Meanwhile, Justice Secretary Kenny MacAskill said today that Scots caught up in the Algerian hostage crisis have been through a "horrendous ordeal",
A second worker with Scottish connections is still missing, feared dead. Three British nationals are now known to have died and three more are believed to be dead. A Colombian-born UK resident is also thought to have died.
Mr MacAskill told BBC Scotland: "We know that eight got back safe and sound, and are now back with their families, apart from one who I think decided to stop off with friends in London.
"But we do believe that two Scots or those with an immediate family connection in Scotland are believed to be among the missing presumed dead."
He said workers from Scotland came from all over the country and Strathclyde Police provided a co-ordination role, such as dedicating a family liaison officer to each family.
"As the victims who have survived come home, they will be in contact to see what counselling can be provided because even those who have survived have been through a horrendous ordeal, as we have seen on the television, and we will be making sure, through police and other agencies, that appropriate contact is provided," he added.
Mr MacAskill also said no-one could have anticipated the "horrendous attack".
He said: "Algeria is a country I know well, having visited myself many years ago and my own father worked there some considerable time back, so I know the country.
"It has ebbed and flowed, it had got better, but there has always been difficulties there and, indeed, as we see whether in Mali or indeed in Libya, both of which are adjacent to Algeria, there are ongoing problems.
"But I don't think anybody could have anticipated such a horrendous attack that has seen the death, not only of those with a Scottish connection or a UK connection, but people from many, many countries around the world, not least Algeria."
BP employee Alan Wright, 37, from Portsoy in Aberdeenshire, is among one of the survivors to have returned to the UK. He was working at the plant when the Islamist terrorists stormed the compound.
The father-of-two hid in an office for 24 hours before joining Algerian colleagues in cutting their way through a fence and fleeing.
He said: "If you have been captured, there's pretty much no escape and it is going to take a miracle to get you out.
"The first cut of the fence, the wire and tension makes such a noise when it breaks and you knew it travelled to where the terrorists were.
"But within 30 seconds they had both fences open and we were free to go, that was it."
It has also emerged that Mr Wright's cousin was working on a rig near the gas plant as the crisis unfolded.
Richard Cormack, 38, of Buckie in Aberdeenshire, said the site a couple of kilometres away lost all contact with the plant.
He said: "We were secure where we were, because of the gendarmes and military security that we had around our rig.
"But the rig was approached on a few occasions and we were all ducking and diving under containers because we didn't know who was coming."
He added: "We're the lucky people who have got out. My heart goes out to anyone who has lost someone."