(CNN) -- Two of three American hikers who have been detained in Iran for nearly 10 months -- Shane Bauer and Sarah Shourd -- have gotten engaged in prison and plan to get married after their release, their relatives said Monday.
The third hiker, Josh Fattal, plans to be best man at the wedding, the relatives said in a statement.
The three hikers' mothers learned of the engagement when they visited Bauer, Shourd and Fattal in Iran last week.
"Shane told me that he proposed to Sarah in the yard of Evin prison on January 6, the very same day that we applied for our visas to go visit them," Bauer's mother, Cindy Hickey, said in the written statement. "We're all so overjoyed at the news but it's obviously impossible to know when the wedding will take place."
The couple wears engagement rings that Bauer made from threads he pulled from his shirt, the statement said.
"Sarah couldn't wait to show me her ring," said Shourd's mother, Nora Shourd. "It's one of the things that keeps her going -- knowing that she and Shane have this unbreakable bond and a friend in Josh who will always be there for them."
Iranian authorities detained the three after they reportedly crossed the border into Iran by accident while hiking in Iraqi Kurdistan.
On Sunday, Iran's intelligence minister said the three Americans are spies, but he hinted that Iran may consider releasing them in exchange for the release of Iranian prisoners, state media reported.
"We expect the Americans, who claim to be advocates of human rights, to also commit humanitarian acts, because only after this can we decide on whether or not to have a swap," Iranian Intelligence Minister Heydar Moslehi said, according to the IRNA news agency.
Speaking on the sidelines of a Cabinet meeting, Moslehi said there had been no official talks about a swap, Iranian state television reported.
The trio made a brief phone call home March 9 and have had access to a few letters and messages sent by relatives, friends and supporters.
They have not been formally charged, although Iranian officials have said they will face trial on espionage charges.
Before their trip, the mothers had requested meetings with Iranian President Mahmoud Ahmadinejad and Supreme Leader Ayatollah Ali Khamenei, but those meetings did not take place, according to the hikers' attorney.