Jonathan and Mary Hannah Adams married, 8 Feb 1899, Salt Lake City, Salt Lake, Utah.

He is a son of John O'Brien and Rebecca Angelina King.

Jonathan was called "Jont" by his beloved wife, Mary Hannah. They were totally devoted to one another.

Both worked together farming the "hollow" bottom land in northeast Layton, Davis County, Utah. They had been childhood friends, both being born in the same village.

Early in their marriage, he got a job at Driggs Idaho at a creamery. In 1893, Samuel Kunz and family had moved there from Bear Lake Valley and established the first cheese-making plant. In 1895 a cheese factory was established in Driggs. The dairy business continued to grow until there were five or six cheese factories in the valley, besides a vast amount of cream being daily exported, and a large amount of butter made. Jonathan had taken some training as a creamery man and cheese maker, so by about 1900, they had settled near Driggs. One family photo of the brothers is captioned "Tetonia Cheese Factory", but it is unsure if that was the actual name.

Their second son, Jonathan "Jack" O'Brien was born at Tetonia September of 1902. It was recorded that someone absconded with the creamery profits, which caused a layoff of the employees. In any case, the O'Briens were back at the farm in Layton by 1903, where their first son, Winfred Haze O'Brien died in June.

By 1914 the first World War had broken out, sending wheat prices plummeting; and, after a series of bad winters and other set backs, the farm was failing. Jonathan decided it would be a great burden on those who would be affected, if he were to take out bankruptcy. He decided to forfeit his holdings, and pay his debts. He worked for other farmers for a time and then became custodian of the Layton Church House on the hill, above the hollow which was once home to them.

Several stories have been told of the Great Depression causing him to loose the family farm, but that event did not even start until a year after Grandpa Jonathan was dead. The pride which drove some family members to tell that tale was not inherited from Jont. His pride was genuine, stemming from his determination to pay his debts, rather than to hold onto the farm through the practice of bankruptcy, which he abhorred.

His honesty took its' toll on his health, as the $8.00 a month job of cleaning and tending to the dirty coal bins and furnace of the Meeting House caused tuberculosis, which took him to a painful and early death.

Their children were - Winfred Haze O'Brien, Jonathan O'Brien, Don James O'Brien, Lester George O'Brien, Daniel Alfonzo O'Brien, Rachel Eliza O'Brien, William King O'Brien, Fonda LaVon O'Brien.