^^That would be a completely different circumstance though.Yes,unlawful presence does apply to the 20 and 19 year old but it does not "void" the applications.USCIS makes an exception to those that have pending applications under the age of 21 whom overstayed their visas and is an immediate relative to a permanent resident parent or US citizen petitioning for their children[generally under 21 for immigration purposes],it is basically an exception to the rule to respect the rights of the person doing the petition.There are many others exceptions such as 245i or Marriage to a US citizen which excuses unlawful presence THUS nullifying the immigration bars.

If you can nullify unlawful presence you can get rid of the immigration bars,but most of what I have mentioned is only possible INSIDE the US.It is the very reason many don't leave AND why US embassies are so strict with regard to letting anyone inside the US because it creates opportunity for permanent stay if applicable and successful.