And 19 percent of respondents reported that another relative or they themselves were no longer in contact with family.

Myth: There’s a Clear Reason People Become Estranged

Multiple factors appear to come into play. In a 2015 study, Dr. Agllias interviewed 25 Australian parents, each of whom had been cut off by at least one child. The reasons for the rupture fell into three main categories. In some cases, the son or daughter chose between the parent and someone or something else, such as a partner. In others, the adult child was punishing the parent for “perceived wrongdoing” or a difference in values. Most parents also flagged additional ongoing stressors like domestic violence, divorce and failing health.

A woman once insisted to Dr. Agllias that she had not spoken to her son and his wife in seven years because she asked her daughter-in-law to bring a specific dessert to a family gathering, and the daughter-in-law had deliberately brought the same one she had baked. The mother-in-law saw it as “a symbol of total disrespect,” Dr. Agllias said, yet she revealed other factors that had undermined their relationship, including that she felt her son’s wife sometimes kept the grandchildren from her and didn’t properly take care of her son. The dessert, Dr. Agllias said, became a symbol of the “cumulative disrespect” she felt.

Myth: Estrangement Happens on a Whim

In a study published in the journal Australian Social Work, 26 adults reported being estranged from parents for three main reasons: abuse (everything from belittling to physical or sexual abuse), betrayal (keeping secrets or sabotaging them) and poor parenting (being overly critical, shaming children or making them scapegoats). The three were not mutually exclusive, and often overlapped, said Dr. Agllias, a lecturer at the University of Newcastle in Australia.

Most of the participants said that their estrangements followed childhoods in which they had already had poor connections with parents who were physically or emotionally unavailable.

For instance, Mr. Maack resented that he was routinely left in charge of his two younger siblings, so much so that he decided never to have children of his own.

After years of growing apart, the final straw was his wedding day.

In 2014, he and his longtime girlfriend decided to marry at City Hall for practical reasons: They realized she wouldn’t be able to inherit his pension, otherwise. He didn’t invite his family, in part because it was an informal gathering. But also because a brother had recently married in a traditional ceremony, during which his father had backed out of giving his speech. He worried that his father might do something similarly disruptive. He did not want to invite him and said he didn’t think anyone else would come without him.