1. You would never know it, but their father was quite a troublemaker in his youth. He sowed his wild oats before he became a family man and an important member of the community.
2. Nancy doesn’t want to settle down to a family and career until she has spent a few years traveling, having a good time, and sowing her wild oats.

The expression has traditionally been used to describe the behavior of a young man (opt.1), although nowadays it can be used to describe young people of both sexes.