These are "starter jobs." They were not meant to pay for a family of four people. These types of jobs hire folks with NO skills...they have no experience....such as high schoolers getting their first "starter job."
Who expects a minimum wage job to support a family of four? Minimum wage jobs are learner jobs, part time to work with school hours etc. They teach you how to work and what it's like to earn. They teach you how to work with a boss and coworkers, build a resume and mostly to encourage you to move up to a better paying job or into a higher position. If minimum wage jobs were above 16 year old ability they would not stay minimum wage.
Minimum wage/living wage staged agitations are a labor union Trojan Horse. Their interest lies in labor contracts that are structurally tied to minimum wage legislation, i.e. a minimum wage increase triggers union wage increases.
To set a minimum wage is to artificially put a value on labor that does not relate to the job. In a non liberal world, all wages would be based on the skill level required to perform the work. If the worker thought he was worth more, then his option was to apply for a job that paid more. This is based on his qualification or lack there of.