Craig and Charlie Reid are supporting this year's Poppy Appeal which is asking people to forgo their takeaway coffee or doughnut and put the cash in a collection tin instead.
Each year the fundraiser helps Poppyscotland support vulnerable veterans and their families with advice, counselling and adaptions to their homes. Last year saw a slight drop in donations.
Craig said: "It's a cause we've always supported and one that means a lot to us.
"Poppyscotland does a fantastic job in looking after ex-servicemen and women, and their families too. The more money that goes in the tins, the more help Poppyscotland can provide. We hope people will get behind this year's campaign."
The Leith-born brothers' grandfather was in the Royal Scots and died in 1940 while serving as a driver in the Second World War. Their father completed National Service in the 1950s with the Scots Guards.
The Proclaimers' biggest hits provide the soundtrack for box-office favourite Sunshine On Leith which has a storyline about young soldiers returning from Afghanistan.
Poppyscotland's head of fundraising, Colin Flinn, said: "There is no doubt about it, times are tough. However, demands on our services are increasing all the time and we need to raise more money to deliver new and existing services to meet the current and future needs of the Armed Forces community in Scotland."
The Scottish Poppy Appeal runs until November 11. People can donate by putting money in poppy tins, donating online at poppyscotland.org.uk or by texting POPPY to 70800.