In Home, On Location, Park, or Outdoor (non-beach) Setting.

Ultimately, your personal desires for the look of your portrait dictate the level of formality.  If the guys in your family are never in the coat-and-tie look, it would be unrealistic to photograph them that way.  Backgrounds and furnishings also play a key roll in selecting your attire. Below is a great example of casual attire in a formal surroundings...but we think it works!

Indoor and outdoor family portraiture at the Ritz-Carlton