There are many different Ancient Chinese sources that label the Three Sovereigns and Five Emperors differently. I personally like to follow the Records of the Grand Historian since there's a lot of trusted documentation associated with it, so in that case you can link Fu Xi as the Heavenly Sovereign.

For those who don't know, I'll expand on Fu Xi since my post isn't very descriptive. Fu Xi was a supposed demi-god of ancient China who was said to invent various things such as writing and fishing. He instituted the concept of marriage and married his sister Nu Wa. There are a lot of folk tales associated with him that credit him with various inventions and writings, his actual existence is highly doubted.

Edit- Just noticed your other topic about the Yellow Emperor. Keep in mind that many sources say different things, a lot of people like to use the Records of the Grand Historian as the main source for these kinds of differences.