O'Fallon, Missouri (CNN) -- Nathan Halbach is 22, with a diagnosis of terminal brain cancer. He knows that "horrible stuff" lies ahead.
His mother, Pat Bond, has been taking care of him full time. But when she needed help, she reached out to the Roman Catholic Church.
After all, his father is a priest.
Nathan was born in 1986, during a five-year affair between his mother and Father Henry Willenborg, the Franciscan priest who celebrated Nathan's baptism. In a story first reported in the New York Times, it was revealed that The Franciscan Order drew up an agreement acknowledging the boy's paternity and agreeing to pay child support in exchange for a pledge of confidentiality.
Now her son -- the youngest of four children -- may have just weeks to live. And when the Franciscans balked at paying for his care, she decided she was no longer bound by her pledge of confidentiality.
"I never asked for extraordinary amounts. I asked for the basic needs and care of my son," Bond told CNN's "AC 360." But she said the church told her, "No, we are not Nathan's biological father, we have no legal obligation to your son."
Willenborg, whose priestly vows require celibacy, has been suspended from his most recent assignment, in northern Wisconsin, as Catholic leaders investigate allegations that he was involved with another woman -- then in high school -- around the same time he was seeing Bond. Willenborg has acknowledged his relationship with Bond, but denies any inappropriate relationship with the other woman while she was a minor, according to his current bishop.
And his order acknowledges its agreement to support his son, telling CNN they have paid about $233,000 to support Nathan over his lifetime. Since the affair has become public, the Franciscan Order has agreed to pick up Nathan's medical bills and the costs for the funeral that now appears likely.
Willenborg refused to speak to CNN. But a statement to his parishioners in Ashland, Wisconsin, in September, said, "My failure to be faithful to my vows has caused me and many others pain and disappointment. I have regretted this for a long time."
And in October, he told The New York Times, "We've been very caring, very supportive, very generous over these 20-something years. It's very tragic what's going on with Nathan."
Bond, then Patricia Halbach, said she and Willenborg began their affair in 1983. At the time, Willenborg was a priest in her hometown of Quincy, Illinois, about 130 miles north of St. Louis, Missouri.
Bond, then a 27-year-old, married mother of three, went to a retreat for women with troubled relationships. Willenborg was the retreat's spiritual director, and she said he was a "terrific" priest -- "incredibly charismatic, very sought-after."
He began to counsel her on a regular basis. After about three months, at the end of one of their sessions, she said he kissed her. Bond said she went home and immediately asked her husband for a separation, and she said she began a romantic relationship with Willenborg.
Bond said she knew he was forbidden to have sex with her. But she said when in love, "You don't think clearly."
"I make stupid decisions in my life," she said. "I am not perfect, far from sainthood, and I loved him."
During their relationship, Bond was a lay leader in the church, and "We were a very good team, a very dynamic team," she said.
But in 1985, she learned she was pregnant. The pregnancy ended with a miscarriage that October. She said in its aftermath, she ended her sexual relationship with Willenborg, only to resume it the following spring. It was during that period that Nathan was conceived, she said.
Nathan was born in December 1986. Willenborg had to disclose the affair and Bond's pregnancy to his superiors. A deal was negotiated by Father Robert Karris, who told CNN the Franciscans insisted on confidentiality "to protect Nathan, his mother, and the priest." But Karris, now on the research faculty of the Franciscan Institute at St. Bonaventure University in Olean, New York, also acknowledged the goal in part was to protect the church.
The agreement was reached about a year after Nathan's birth. Afterward, Willenborg was removed from his job, and it was 17 years before he would lead a congregation again. He told his superiors that his relationship with Bond was over, but she said it continued.
"That was the statement, and they bought it," Bond said. "But the truth of the matter is during those eight month of negotiations, we were living together physically, sexually and every form of relationship there was under their nose."
The relationship went on until Nathan was nearly 2 years old, Bond said. She and Willenborg went on family outings, including a trip to Florida, with Nathan and her children from her previous marriage. Back in Quincy, where she grew up, Bond said she had a simple answer to questions about Nathan's parentage: "He's my baby."
But things ended in 1988, after Bond learned that Willenborg was seeing another woman. She eventually moved from Quincy to a St. Louis suburb.
"You had to go away, you had to take your story, you had to take your children, you had to get out of this town. We're a small community, everybody knew everybody," she said.
Nathan grew up as a popular, athletic boy, a big fan of the St. Louis Cardinals baseball club and the Blues hockey team. He has autographs of the entire hockey team and a Cardinals uniform signed by All-Star first baseman Albert Pujols.
For years, he said, he wanted a relationship with his father.
"He's popped in and out of my life, but I've never gotten the full respect and love out of him that I would always want," he said. But several years ago, after Willenborg took him out to dinner on their first night out in years, he said his father didn't seem to want to have anything to do with him.
"When it comes to this person who's my dad, who should be helping me out more than a person on the street, he hasn't done so throughout my 20-plus years of life," Nathan said.
Nathan was diagnosed with cancer in 2006. Over the summer, he and his mother went to New York's Sloan-Kettering cancer center in a last-ditch effort to halt the disease. It was unsuccessful, and doctors give him a prognosis of weeks.
"If I just live my life as happy as I can, I can have a lot of fun until this horrible stuff happens," he said.
The church had paid for some medical expenses and gave her $1,000 toward travel expenses for the trip, but not room and board or treatment costs, Bond said. And in the past week, she said, the church was questioning the cost of a looming funeral.
"They were concerned with getting us out of their lives, and I guarantee you, the day my son goes, the church will rejoice," she said.
Since she went public, the Franciscans wrote a letter to Bond telling her they will cover 100 percent of her son's funeral costs -- and added, "Please advise if there is any additional assistance that the Franciscans can provide to Nathan at this time in connection with his day-to-day expenses and comfort." The order also has since said it will not take Bond to court for breaching the confidentiality of the agreement.
For four years before September, Willenborg was a priest at Our Lady of the Lake church in Ashland, Wisconsin. Bishop Peter Christensen, whose diocese includes the church, said Willenborg was a good priest -- but added, "Because of his behavior 23 years ago, the community is now suffering."
Nathan will not be going back to the hospital and will die at home, Bond said. She can't afford a part-time nurse to help take care of him in his last days, but said she hopes the church lives up to its word.