Multigenerational living, where two or more adult generations live under the same roof, is becoming a growing trend in the U.S. Currently about 19% of Americans now live in a multigenerational household, the highest level since 1950. That amounts to about 60.6 million adults in 2014, up from 57 million adults in 2012. And homebuilders have taken notice, designing houses specifically catered to this segment.