Family is traditionally defined as a group consisting of parents and children living together in a single household, but a new study by Munich-based Allianz renders that definition obsolete.

In “LoveFamilyMoney,” a survey published on Monday, Allianz found that the number of households currently comprising the traditional heterosexual couple with children is currently fewer than one in five, a significant decline since 1970, when 40.3 percent of households comprised such families.

Allianz’s findings suggest that traditional families are still one of the backbones of American life. Most of these households said they were financially healthy, with 64 percent of respondents indicating they were on track to reach their financial goals. But 73 percent identified themselves as spenders rather than savers, the highest reading of all cohorts. Only 33 percent of them have a college savings plan in place.

Traditional families are also more likely to work with financial professionals than “modern families.” Allianz identified six types of the latter category: same-sex couples, single-parent households, households with adult children returning home, families with multiple generations living under the same roof, blended families and families with older parents and young children.

Overall, more than half of the modern families surveyed felt like they were on track to meet their financial goals. Seventy-six percent worry about running out of money in retirement. Only 43 percent have worked with a financial professional.

Of the same-sex couples surveyed, more than one-third, 35 percent, have at least one child in the household. Nearly one in four, 24 percent, carry no debt beyond their mortgage. Same-sex couples were the most affluent family types studied by Allianz, with those respondents reporting a mean household income of $113,700. (Such households made up 12 percent of the study’s total respondents.)

Most single-parent families, 56 percent, exist by choice. Anxiety pervades these households: 84 percent agreed with the statement that “single parents have it harder financially than dual-parent households.” Just 21 percent of single-parent families are saving for their children’s college education. Single parents made up 12 percent of Allianz’s respondents.

Households with adult children returning home, also known as boomerang families, were among the most financially secure, consisting of 13 percent of the respondents. More than two-thirds of these, 68 percent, described themselves as savers, not spenders, and 51 percent reported being debt free. Most parents, 54 percent, said they would prefer their adult children to live with them for as long as they want, and 45 percent of parents expect nothing back in exchange for allowing their adult children to live at home.

Multi-generational households made up 12 percent of the survey’s respondents, and these families are nothing new. Forty-nine percent said they grew up in a multi-generational household. Most of these families’ situations come about because of a health issue with one member (in 49 percent of the cases). Otherwise these households are formed for financial reasons (in 44 percent of the cases). Multi-generational families were the most likely to worry a great deal about planning for future financial needs (something 33 percent of them worried about).

The formation of blended families may exacerbate the anxieties of single parenting rather than solving them. One in five survey respondents lived in a blended-family household. Most parents in these families, 79 percent, are stressed about planning for their future financial needs, and 43 percent said that they or their spouse had brought financial baggage to the relationship that was difficult to overcome. Blended families were the least likely to feel on track to achieving their financial goals (only 46 percent said they were).