Hey,
this page states, that Rubens is a variant form of Reuben, whereas the brazilian websites I usually consult state, it is not a variant of Reuben (that would be Rúben or Rubem) but derives from Latin "rubens" meaning "red".
I couldn't add this as a user submitted name. I wondered, why that is.
BTW: The pronunciation of Rubens is: /ˈhubẽjs/
Links:
https://www.dicionariodenomesproprios.com.br/rubens/
https://nomes.clickgratis.com.br/meninos/r/significado-do-nome-rubens.html
https://www.fetalmed.net/ferramentas/significado-de-nomes/nome/rubens/
https://baiadoconhecimento.com/biblioteca/conhecimento/read/290589-qual-a-origem-e-significado-do-nome-rubens