The alien family togetherness EO today clarifies that only real parent-child alien families stay together, not uncle-nephew or pedo trafficker-child slave "families":

(b)  “Alien child” means any person not a citizen or national of the United States who

[…]

(iii)  has a legal parent-child relationship to an alien who entered the United States with the alien child at or between designated ports of entry and who was detained.

Also gets the Department of Defense involved in providing and building holding facilities:

(c)  The Secretary of Defense shall take all legally available measures to provide to the Secretary, upon request, any existing facilities available for the housing and care of alien families, and shall construct such facilities if necessary and consistent with law.  The Secretary, to the extent permitted by law, shall be responsible for reimbursement for the use of these facilities.

https:// www.whitehouse.gov/presidential-actions/affording-congress-opportunity-address-family-separation/