Clinton signed an aggressive crackdown on illegal immigration in 1996. It neither allowed nor forbid separating families. it simply doesn't address the issue whatsoever.

In 2008, President George W. Bush focused on the problem of minors crossing the border without their parents and signed a law unanimously passed by Congress that called for such "unaccompanied minors" to be released into the "least restrictive setting."

By 2014, President Barack Obama was facing an influx of both children travelling alone and families as a result of violence in Central America. At one point, his administration tried housing the families in special detention centres. But after a federal judge in California ruled the arrangement violated a long-standing agreement barring kids from jail-like settings, even with their parents, the government began releasing families into the U.S. pending notification of their next court date. http://www.cbc.ca/news/world/us-immigration-fact-check-1.4711267