First of all we are not enough capable to translate each and everything correctly, but if you go through all the Puranas you will find one thing in common, the Param Brhama in creation devided itself into two parts, Purusha and Prakrati, the Purusha itself is the Tridev, the Brahma, Vishnu and Mahesh.

The Prakrati is the universe, everything as the part of universe i.e. galaxy,planets,plants,animals and atoms, as universe is finite but Prakrati is not a lot of energy was left out after creation, this left out infinite energy was the cause of creation of Lakshmi, Saraswati and Parvati(Sati). All three came into creation by same physical word if you go deeper into Brahma's Creation.

This might not fulfill the answer because, we are of meager brains, we need to learn a lot to translate and get the actual meaning of Puranas correctly.

Last thing most of english translation are invalid, so don't give a lot of emphasis on them, I have read an altogether different story which says,

There was a fight between Rakshasas and Devas, where Devas were overpowered, and they went for help to Tridev, among-st which Shiva fought with the Devas, but Brahma just watched it. When Rakshasas were overpowered they started fleeing on which the fifth head of Brahma suggested the Rakshasas to return to battlefield and fight Shiva, this made Shiva angry and he tore of his fifth head.

In relation to incest, I already explained that Brahma is a Purusha part of Param Brhama, and Saraswati is a Prakrati part of Param Brhama, therefore they will naturally attract as matter and anti-matter. But the word incest is actually limited towards biological beings, and it cannot be used to define the relations of Atman. To Describe it more, there are two types of Reproduction, Sexual(found in mammals) and Asexual(as in amoeba) and the asexual, the intial creation of Brahma all reproduce Asexually. And foremost we even cannot call Saraswati as daughter of Brahma, she is Prakrati(matter) and Brahma is Purusha(anti-matter), both with opposite nature.

Even we are attracted towards the Tridev, because they are Purusha and we are Prakrati.

First of all we are not enough capable of translating each and everything correctly, but if you go through all the Puranas you will find one thing in common, the Param Brahma in creation divided itself into two parts, Purusha and Prakriti, the Purusha itself is the Tridev, the Brahma, Vishnu and Mahesh.

The Prakriti is the universe, everything as the part of universe i.e. galaxy, planets, plants, animals, and atoms. As universe is finite but Prakrati is not, a lot of energy was left out after creation, this left out infinite energy was the cause of the creation of Lakshmi, Saraswati, and Parvati(Sati). All three came into creation by same physical word if you go deeper into Brahma's Creation.

This might not fulfill the answer because we are of meager brains, we need to learn a lot to translate and get the actual meaning of Puranas correctly.

Last thing most of English translation are invalid, so don't give a lot of emphasis on them, I have read an altogether different story which says,

There was a fight between Rakshasas and Devas, where Devas were overpowered, and they went for help to Tridev, amongst which Shiva fought with the Devas, but Brahma just watched it. When Rakshasas were overpowered they started fleeing on which the fifth head of Brahma suggested the Rakshasas return to the battlefield and fight Shiva, this made Shiva angry and he tore off his fifth head.

In relation to incest, I already explained that Brahma is a Purusha part of Param Brahma, and Saraswati is a Prakriti part of Param Brahma, therefore they will naturally attract as two opposite type of energies. But the word incest is actually limited towards biological beings, and it cannot be used to define the relations of Atman. To Describe it more, there are two types of Reproduction, Sexual(found in mammals) and Asexual(as in ameba) and the asexual, the initial creation of Brahma all reproduce Asexually. And foremost we even cannot call Saraswati as daughter of Brahma, she is Prakriti(matter) and Brahma is Purusha(anti-matter), both with opposite nature.

Even we are attracted towards the Tridev, because they are Purusha and we are Prakriti.