NEW YORK (TheStreet) -- The so-called nuclear family is in decline, and some of the financial blessings of their era may be going by the wayside too.

The nuclear family model was classically an opposite-sex married couple with children. In 1970, that was 40.3% of all U.S. households. Today that figure has declined to 19.6%, according to data from Allianz and its LoveFamilyMoney Study released this week.

In its place are more of what sociologists call the "modern" family, which Allianz breaks down as follows:

Multi-generational families:Three or more generations living in the same household.

Single-parent families: One unmarried adult with at least one child under 18 years of age.

Same-sex couple families: Married or unmarried couples of the same gender.

Blended families: Parents who are married or living together with a stepchild and/or child from a previous relationship.

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Older parent with young children families: Parents age 40-plus with at least one child under 5 in the household.

Boomerang families: Parents with an adult child (age 21 to 35) who left but later returned to rejoin the family.

While the household unit evolves, Allianz points to a potentially big trouble spot: They're experiencing problems managing their money compared with traditional family households, with 57% of U.S. modern families "struggling to make ends meet," "struggling financially" or considering themselves "poor." That 57% figure is 10 points higher than that cited for traditional families. (Of course, financial difficulties are undoubtedly the reason many of these modern families exist.)

Just under half (49%) of modern families say they are living paycheck to paycheck, compared with 41% of traditional families.

Some additional data from the study:

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  • 30% of modern families felt a high level of financial security, compared with 41% of traditional families.
  • 36% of modern families have collected unemployment, compared with 21% of traditional families.
  • 35% of modern families have unexpectedly lost a main source of income, compared with 23% in the traditional category.
  • 22% of modern families have declared bankruptcy, compared with 11% of traditional families.

"New family structures have a direct impact on a family's relationship with money and finances -- and we found that, while modern families have similar strong emotional ties, they often feel financially less secure than their traditional counterparts," says Katie Libbe, a vice president at Allianz. "While family structure plays a prominent role, our study of these different modern family cohorts uncovered a number of unique insights into each group's attitudes, perceptions and beliefs around money and financial planning."