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You are not able to parent both hands to a prop, or a prop to both hands. You will need to manually pose the second hand according to the position of the first hand and its child prop.

I remember in another thread I made here afew months ago on a different subject, someone mentioned it was possible to use IK to link the figure to an object

Would it be possible to parent the right hand, and use IK for the left?

Adjusting manually will probably lead to strangeness and inconsistency.