Uniting Families Act of 2019 This bill establishes a non-immigrant visa category for an alien who (1) is 18 or older and is the genetic son or daughter of a U.S. citizen who served in the Armed Forces on active duty abroad; or (2) is the spouse or child of such alien and is accompanying, or following to join, such alien. To obtain a visa, the alien's citizen parent must petition and receive approval from the Department of Homeland Security. The petition shall include (1) DNA evidence establishing the parent-child relationship, (2) a written statement that the parent will provide financial support until the alien receives lawful permanent resident status, and (3) proof of the parent's U.S. citizenship and active duty with the Armed Forces abroad. The period of authorized admission for aliens with the visa is five years, and 5,000 principal visa aliens may be admitted per fiscal year. Holders of such a visa may adjust to lawful permanent resident status after meeting various requirements, such as being admissible as an immigrant.