Facebook's minimum pay is double the national minimum wage. And the two parents in question earn above this. If both parents work a full week, they're on the equivalent annual salary of $39k and $37k, so $76k a year household income, excluding any welfare benefits or subsidies they could get in addition to their wages.
The average US household income is $56k, so they are well above the national average.
The issue they face is housing prices, not salary or their household income. And if you live in an area with huge growth or a rising housing bubble, wages for the vast majority will never match the rising cost of property. The woeful US health system is another issue, but not something they can hold against Facebook or any other corporation.
In this instance, I don't know what they want from Facebook, who already pay well above the national average across the board. They're unskilled workers, who live in one of the most expensive area in the US. They face a reality that millions of families living in expensive cities around the world also have to face. Whether their income and skills allow them to live in areas that grow in desirability and price year-on-year.
I live in one of the most expensive cities in the world, and even though I have a decent salary, my family and I had to move way out into the suburbs for us to afford property. I have a big commute each day, a trade off I was willing to make to continue living in the this city. A 10%, 20% or whatever pay increase for me wouldn't make a dent in the ever increasing house prices if I wanted to buy somewhere closer to the city. That's the reality.