Giyuu was born into a family that are so weird. He was born against his mother's wishes.

Muzan Kibutsuji, Aka the demon lord has had 4 wives( Later it will be 5)  and kill them all because they no longer valid for use. Giyuu's existence is beyond Muzan's guess. It is known that Muzan only learned of Tsutako's existence and ordered someone to kill her.

______________________________________
Kibutsuji Mansion

"

Agh!" Okako protected little Tsutako from being slashed, as she had previously told her to hide Giyuu

"OKA-SAN!" Tsutako sobbed, but was forced to run and hide Giyuu far away from him while Okako was stopping Muzan

Muzan:"Let me go you b-itch!" He slashed Okako's body with a life-or-death blow with his kagune
"Tch, Letting it escape again, what an b-itch"

______________________________________

Tsutako ran through the forest and gasped, holding 1-month-old Giyuu. Her face was sobbing and Time past, Giyuu and Tsutako were adopted by a family but unfortunately they both got sick and passed away, leaving Tsutako and Giyuu behind when he was 13 year old. He was a former water pillar, He was trained as a Hashira .

__________________________________
Fun fact: Giyuu and Sanemi village near each other