[LifeStyle] Bill and Melinda Gates are the latest couple to get a 'gray divorce.' Here's why more married people part ways after 50.

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On Monday, Bill and Melinda gates announced their divorce, putting an end to their 27-year marriage.

Bill and Melinda have now joined a growing number of older couples filing for "gray divorce," or a marriage dissolution later in life.

In 2015, the National Center for Health Statistics and U.S. Census Bureau compared divorce rates from 1990 and 2015 and found divorce rates doubled for those who were 50 and older. People 65 and older were three times more likely to get divorced in 2015 compared to 1990.

The rise in later-in-life divorces can be attributed to marriage dissolution becoming less taboo, a fixation on child-rearing, and people living longer, according to Barry J. Jacobs, a clinical psychologist and co-author of the AARP book "Love and Meaning After 50: The 10 Challenges to Great Relationships — and How to Overcome Them."

People are living longer and growing apart

Generally, married couples today have the same level of relationship satisfaction as previous generations, Susan Brown, co-director of the National Center for Family & Marriage Research at Bowling Green State University, told Thrive Global.

But today's humans have longer lifespans, which could explain a rise in divorce for the baby boomer generation, said Brown.

Today's 65-year-olds can live, on average, until they're 84, Washington Post previously reported. 

As baby boomers grow older, reevaluate their priorities, and gain a greater sense of self, they realize their spouse isn't someone they want to be with for the next 20 years.

 "That's a long time to spend with someone you're not that into anymore," Brown told Thrive Global.

Divorce is more accessible and less taboo

Divorce has also become more commonplace and people feel less shame around marriage dissolution, according to Jacobs.

Until 1969, divorce was only granted if one spouse could prove the other was at fault, like for physical or emotional abuse or infidelity.

But when no-fault divorces, or divorces that could be filed for any or no reason, were legalized over the next decade across the US, an increasing number of baby boomers, children at the time, witnessed their parents split up, National Affairs previously reported.

"They were the first generation whose parents got divorced. Divorce doesn't seem like this tragedy in their lives. It's almost seen as part and parcel of normal family life," Jacobs said of the shifting mentality.

There isn't a roadmap for married life after children

Finally, the American nuclear family isn't structured to prepare parents for life after children, Jacobs said.

A married couple with children often dedicates their lives to raising a family and places less importance on their romantic relationship. Once those children leave home, an older couple may realize they've lost their "sense of common purpose," according to Jacobs.

"[When] spouses, who haven't really been engaged with one another because they've been engaged with the children for a long time, have to turn towards one another and talk all this through, it's very difficult," he said.

In Jacob's experience, baby boomer couples who can't agree on how close to live to their children and grandchildren or how they want to spend their retired years will choose to part ways so they can live on their own terms.