Ever since learning to use TTL flash, it's become my main method for lighting not only seniors and kids, but also families. While the size of the light ideally should be larger for a family, it doesn't have to be. I have a 4 foot softbox that I'll use for large families (many people... not large people). But for smaller families, I love the Larson 22 inch softbox because I can light them easily and accurately using the TTL metering system in my Canon cameras and Canon 600EX RT.
If I need an extra stop of light, I can place two flash units in the softbox, using a new modification I made to its design.
As you can see by the two examples here, flash WAS needed! There were very few locations at this client's home where I wouldn't have needed auxiliary light. Not because there wasn't "enough" light. It's that it was all coming from the wrong direction... straight up. They live in a woods.
It's important to photgraph people in THEIR setting. Having control over proper portrait lighting gives me the freedom to work whevere I want to. I'm not restricted by having to work where the light is good. A "natural light photographer" would have said, "Let's go to the park where I always go". :)