Rigging horizontally swivelling hinge - plus rotation parenting with offset

Any suggestions greatly appreciated. I’m trying to rig a device which is like two swings which are connected to eachother in the centre with a hinge/pivot which only swivels horizontally. One swing follows the rotation of the other but with an offset. Apologies if I haven’t explained this well. Thanks in advance for any help.

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Viewed from side and behind:


You are showing the offset swing as a one object with object center at the hinge. Can’t you just rotate it by the origin along the hinge axis?