Tai Yang and Tai Yin can share Chou or Wei in the standard major-star arrangement. The same pair name does not make those placements identical. Traditional brightness assessments depend on position and may differ in detail across schools.
Examine each star's conditions
The Sun carries outward-expression and contribution themes; the Moon carries accumulation, detail, and inner-experience themes. A same-palace reading should examine their conditions and supporting stars rather than assigning someone half an extrovert and half an introvert.
Several traditional pattern names also refer to different arrangements. Sun and Moon sharing a palace is not the same condition as flanking the Life Palace or meeting a specified bright-Sun-and-Moon pattern. Similar names should not substitute for checking actual positions.
Avoid overly easy confirmation
Imagine a person who speaks publicly at work and prefers quiet research at home. These observations can supply material for discussion, but both behaviors are common. Their coexistence does not establish chart accuracy.
A more useful question is which environments support sustained work and which responsibilities are draining. Compare those experiences with the relevant palaces rather than stopping at an attractive pattern name. Identify Chou or Wei, assess both stars, and then examine transformations and connected palaces.