I keep hearing this, but according to TJs:
Who owns Trader Joe’s?
Trader Joe’s is owned by families that also own part of Aldi Nord. Trader Joe’s and Aldi Nord operate independently. Trader Joe’s has no business or ownership relationship with Aldi Sud (including Aldi U.S.).
Wikipedia (fwiw) says either Aldi Nord or the Albrechts are owners, depending on whether one is reading the article about Aldi or Trader Joe’s.