You can start by looking on fanfiction - dedicated websites like Archive of Our Own (AO3). There are likely to be a good number of stories there tagged with relevant keywords like 'Cole Turner' and 'Charmed Niece'.
Another option is to check out some Charmed - specific fan communities on social media platforms like Reddit or Tumblr. Often, members of these communities will share or recommend great fanfics that involve Cole Turner and the Charmed niece.
Chapter 913, "Call Me Daddy", is the clearest early answer because it turns Meng Wanzhi's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Meng Wanzhi woke up early, preparing to get the two little rascals up...
Chapter 929, "Award Ceremony", is the clearest early answer because the buildup finally cashes out in a real clash. The chapter turns that into something concrete by moving from The Golden Statue Award is considered the most prestigious award in...
Chapter 874, "All the Same", is the clearest early answer because it turns Xiao Ni's situation into a concrete plot event. A useful checkpoint is the way the scene starts with This family is surnamed Shi, and they have lived in this village for...
Chapter 718, "This Person Is No Longer the Same Person", is the clearest early answer because it turns Chang Song's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Changqing noticed her amazed gaze and his eyes also shifted to the...
Chapter 802, "Gone Again!", is the clearest early answer because it turns Bufan's situation into a concrete plot event. It opens with Have you checked the fifth floor? and closes on The moment it happened, the old man instructed everyone not to tell....
Chapter 809, "Specially Made for You", is the clearest early answer because it turns Jiang Bufan's situation into a concrete plot event. The chapter gives readers a real answer by opening on Listening to the cries from inside the house that sounded like a pig...
Chapter 858, "If You Dare, Take It", is the clearest early answer because it turns Jiang Buchen's situation into a concrete plot event.
Chapter 35 is the strongest chapter-level answer because it starts from Shining Transformation Trip's filming location was set on the distant... and follows through on Brother is really hardworking, actually arriving at the same time as the....
A practical answer is Chapter 49, because it turns the idea into a concrete scene. The chapter opens with My phone!!!" Jiang Yan's roar echoed continuously through the mountains in..., adds pressure through The guest with the highest score will receive a series of resources from..., and ends on.