The Brothers Yin and Yang also known as their individual bodies as Lord DC and Lord Marvel aren't before or after the retcon's to be the The-One-Above-All and The Presence as they are under their control since both are a Non-Canon Megaverse within Marvel and DC Omniverse respectively.
The Brothers Yin-Yang were once merged for a short time by the combined Combined Nigh-Omnipotence powers of the The Living Tribunal and Spectre which kept them at bay for a few moments which felt like to their Amalgam Megaverse billions of years passed until the Retcon into being the Experiments of The Living Tribunal and Spectre.