Actually it's the independent board of B&J, which has the right to speak out on social issues under their contract with Unilever. The retired founders themselves have also spoken out about the Gaza genocide, separately.
Here's another source, which gives a pretty good breakdown of the corporate situation, despite being a Jewish publication. Perhaps because a lot of Jews are against what Israel has been doing. As they note, Ben and Jerry are themselves Jewish.
Yes sadly Unilever is the parent company of B&J. As much as I would love to support B&J , Unilever is heavily invested in Israel. Unilever even fired the B&J CEO despite promising freedom of political expression of the brand.