It isn’t mentioned a lot for obvious reasons, but Venture is trans, but labeled with non-binary so people wouldn’t be extremely transphobic (Or I assume thats the reason)
It was stated they’re trans in their character concept development blog. If I can find it I’ll post it here.
Edit: found it.
”This personality ended up meshing really well with Venture’s gender identity. Venture is our first trans non-binary hero, and they use they/them pronouns.”