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I had 2 business websites & it became an issue because our backlinks were all from the same sources & were competing & I do not believe Google liked us being 1 business with multiple websites. We combined ours into 1 & it's going well as we managed to retain rankings. If it's a business website you have then in my opinion you should keep things the same as more & more people are creating multiple websites & Google will eventually be forced to act against it. I type this as someone who battles a Competitor with 5 websites. Personally I think your rankings will nosedive as your homepage will be thin content & Google won't like the new domains with no authority or backlinks. I'm no expert but i'very been around the block. What has prompted you to want to split the domains?