A woman has discovered a dark family secret in a bundle of lost letters from the early 1900s – an affair between a woman and her fiancé’s best friend.

Chelsey Brown, 28, from New York City, US, finds diaries, letters, and family heirlooms and reunites them with the descendants of those behind them.

But when she came across her most recent find, she was left unsure about whether to return them to the family, worrying that the knowledge of the affair could cause heartbreak.

“The letters revealed an affair that happened between a wife and her fiancé’s best friend,” she told Jam Press.

“This affair happened during their engagement and probably into the early years of their marriage. I will say, there is more that the letters revealed that I am not saying in public, due to protecting the identity of the family, but it was definitely a love triangle.

“It felt like a heavy weight. It’s hard to explain. This weight is something I carry with any artefact that I handle that reveals sensitive or emotional information about a family.”

Chelsey found the letters through a vendor in California, who she works with regularly to source artefacts.

After reading through the letters, she was able to date them to between 1908 and 1911, and she was amazed by the details.

But realising the secret that the letters could expose, Chelsey did more work to track down the family history, and while she was still deciding what to do, she asked her 90,000 followers on her Instagram page for their thoughts.

People were quick to make suggestions that might help her, while more than 5,000 people liked the clip.

One person wrote: “Maybe reach out to the family and explain that there could be some sad/unknown information in the letters? So they can decide if they want to read the letters.”

Another added: “You were told or read a secret. The universe is trusting you with it. If someone told you a secret about themselves that would hurt others… I doubt you would tell. No good can come of it. Don’t tell.”

“I would give them. I feel like every family has some secrets and this could explain so much. Maybe try to find a younger generation of this family that is a bit removed from this relationship if possible,” another user commented.

Someone else said: “I'd be interested to see those of they were my family. I say reach out!”

Another user added: “Leave it alone. It was so long ago that it will only create sadness.”

Chelsey is still on the fence.

She said: “I am still deciding what I want to do with these letters, but from everything I know about the family, which I found through myheritage.com, I am leaning towards no.

“I really do think it would cause more harm than good, and my mission with these heirloom returns is to gift families with a piece of their ancestors that won’t cause pain.

“With all of the lovely dovey heirloom stories and returns I post on social media, I think people don’t realize that most of the work I do is emotionally heavy.

“Many of the artefacts that I handle deal with affairs, death, family drama, scandal, etc. This is the reality of heirloom work. Some of it is beautiful and some of it is painful. That is why I decided to share with my followers, and it seemed like they found value in it.”

Although Chelsey has been involved with many happy stories of people being reunited with objects from their family’s past, she has to make a personal choice with each one.

She said: “My mission is to get these items back to the families unless I deem the items not fit to return to the families, for example, love letters that are too graphic or letters that reveal information that would cause more harm than good.

“In the end, it is my decision whether or not an item goes back to a family and I try to use my best judgment. Sometimes, a family secret only lives with me - and I know it's my burden to bear.

“My dad is a genealogist and sometimes I will employ his opinion with certain items if it comes down to that. If I decide not to return an item (which is very rare), then I archive them to hopefully one day memorialise these people in some way.

“I do return many ‘sad’ heirlooms, for example, diaries of sad accounts, death notices, and war documentation, but I return these items knowing it will help families heal, deliver invaluable information for family trees, etc.

“There are just some items that, I believe, were not meant to be found and seen by family, and I just happened to stumble upon them by chance.”

Despite the difficulties that come with working with these artefacts, Chelsey loves being able to find out more about the stories.

She said: “I am honoured to be given the title of today's ‘heirloom hunter’ or ‘heirloom detective’ and my mission is to employ others to pick up the same hobby.

“Genealogy and history is fascinating, and it proves that there’s magic behind the lives of average people.”