Dancing Across the Universe

Looking for a Book, Please, Please, Please! ( ๑ŏ ﹏ Ŏ๑ )

I remember this was a quick transmigration story. In the first world, the protagonist became the main character's son and had a younger half-sister (I think). In the second world, they became the main character's sword spirit. Later, when the Immortal Venerable was going through a trial, they took a blow for him.