There's a huge segment within the wealthy part of the U.S. population that feels underserved when it comes to financial advice, and that segment is growing, Financial Advisor magazine writes. Non-traditional families with at least $5 million in investable assets now make up almost the same number of households as traditional families.

The term "non-traditional" covers a wide spectrum of households, including same-sex couples, "blended" families that have stepparents and stepchildren, and multi-generational households, according to the magazine. But, for the most part, they have something in common. Among investors surveyed in June for UBS Wealth Management's "Beyond the Picket Fence" study, cited by the magazine, 70% feel like financial advice is only for the traditional mom-dad-children households. Yet these nuclear families now make up 35% of households with $5 million or more to invest, while the non-traditional segment is 34%.

And the balance is likely to shift soon, going by UBS data cited by Financial Advisor. Traditional families are disappearing: They make up 46% of World War II–era families, 37% of the baby boomer generation, and just 25% of millennials, the survey reveals.

Non-traditional families present their own unique challenges. With the SCOTUS's passage of the marriage-equality ruling, for example, 72% of same-sex couples are looking for guidance on how the law affects their finances, while 60% feel like there's not enough financial advice available to couples like theirs. Furthermore, one-quarter of the same-sex couples believe their parents' lack of acceptance of their orientation may affect their inheritance; and because few such couples have children, they have legacy-planning issues as well, the magazine cites the report as suggesting. Meanwhile, the study shows that multi-generational households, particularly ones with an aging parent or grandparent, have their own set of problems: 56% deemed retirement planning "somewhat complicated," compared to 42% of households without elderly relatives.