Granting citizenship rights to 700,000 Dreamers really means giving a foothold in the U.S. to perhaps 1.5 million other future immigrants, according to analysts who urged Congress to weigh the implications fully before pressing ahead with a mass legalization program.

Chain migration — the ability for the Dreamers to sponsor relatives, including their parents who broke the law by bringing them to the U.S. — is one of a number of issues President Trump and congressional leaders will have to work out as they reach for a deal on Deferred Action for Childhood Arrivals, the Obama-era amnesty that the administration is phasing out.