Ancestry World subscription has a number of documents in addition to the birth record: death record for Max, several border crossings from Mexico into the US, US naturalization papers (original) for Juan. Once public libraries reopen, many have library subscriptions to Ancestry and you should be able to access free.
birth of Juan (m) and Raquel (f) twins b. 10 Oct. 1923 in Mexico City. Birth registered in 1926. Father Max Greenberg and mother Maria Allerhard. It's a very long entry in Spanish and my Spanish is rusty.
death of Max Greenberg: age 70, died 1936. wife Maria Alerhard. Parent Nojiun and Basia.
On two different El Paso border crossing in 1933 Max is listed as b.c. 1876 Vlodorka/Valenda, Poland. Wife Maria.
In all of these records there's more to translate. There are also more El Paso border crossings.
There's a 1944 declaration of intent for John Allegant Greenberg (Juan Greenberg) in the Western District of Texas. He was born 10 Oct. 1923 Mexico and emigrated in 1939.
Border crossing at El Paso 1934 for Raquel. going to cousin Jake Ellegant in Chicago. Looks like a temporary visa.