According to site linked below - "The statistic shows the number of illegal immigrants living in the U.S. from 2000 to 2012, as estimated by the Department of Homeland Security. As of 2012, about 11.4 million illegal immigrants were living in the United States."
We don't know the percentage of those being of age - NOT CHILDREN - but one would imagine, large fams that these folks have - to be more than half.
Thus your claim - 20-30 million illegals is HORSESHT.
Likely number who COULD pass a a voter to be 3 million. One TENTH of your horsesht claim. You just keep getting your ass handed to you here boy.
https://www.statista.com/statistics/257779/estimated-number-of-illegal-immigrants-in-the-us/