Jetpack’s Widget Visibility only supports “Include children” which covers direct children (1 level deep). It doesn’t include grandchildren, great-grandchildren, or deeper nested pages.

This plugin adds an “Include all descendants” option that includes ALL levels of nested pages — grandchildren, great-grandchildren, and beyond.

Features:

Show/Hide widgets based on conditions
Page visibility with full descendant support
Category visibility with hierarchy support
Hierarchical custom taxonomy visibility with descendant support
Post type conditions
Special pages: Front page, Blog, Archive, Search, 404
User role targeting (any selected role)
User state: Logged in / Logged out
Multiple conditions with AND/OR logic
Jetpack-free — no dependencies
30 languages included
Follows WordPress coding standards

Supported Languages (30):

Turkish, English, Spanish, German, French, Italian, Portuguese (Brazil), Portuguese (Portugal), Dutch, Polish, Russian, Japanese, Chinese (Simplified), Chinese (Traditional), Korean, Arabic, Hebrew, Swedish, Norwegian, Danish, Finnish, Greek, Czech, Hungarian, Romanian, Ukrainian, Vietnamese, Thai, Indonesian, Hindi, Slovak

Cybokron Advanced Widget Visibility