Lorna McInnes, who lives in Blairgowrie, said her brother had not given permission for others to handle his finances.
She said the family are now seeking legal advice.
“It is now eight weeks since Fergus went missing in Switzerland and we remain perplexed by his disappearance. While we continue to wait for news, the priority for us now is to look after his affairs.
“In Scotland, unless a missing person has already granted power of attorney to someone else, looking after their affairs in their absence can prove quite a challenge.
“Like most people, Fergus has a number of contracts with different organisations banks, utility companies, memberships, subscriptions, etc but he has not granted power of attorney to anyone.
“This limits what his next of kin are able to do on his behalf, but we have taken legal advice about how best to proceed.”
Family left in legal limbo after man’s disappearance in Switzerland