If you have seen Winter's perspective on Team RWBY on the RWBY Chibi episode: "Kids vs Adults vs Pups" then you would understand this story
Ruby loves her teddy bear. She is always shown holding her teddy bear in one hand and sucking her thumb with the other hand.
That teddy bear made her happy. Her dad would always make it dance like a puppet when she's sad or she would hug it in her sleep to keep her company from the Grimm under her bed or in her closet. She would also make it ride on Zwei.
Yang always loves to tease her baby sister by playing peekaboo, booping her nose or laugh at her when she falls down when she tries to walk to her or her dad.
One day, Yang accidentally took her teasing too far when she took Ruby's teddy bear and held it above her reach. After multiple failed attempts of reaching for her teddy bear from her older sister, the silver eyed baby began to cry.
"WAAAAHHH!" Baby Ruby cried. Her wailing was so loud that the vases and glass from the windows and picture frames cracked and shattered.
Tai then comes to the living room with his ears covered and says "Yang, what's going on here?"
"I was just teasing Ruby as usual" the little brawler said.
"Yang, you can tease her with all the peekaboos, nose boops or laugh when she falls down when she tries to walk to you or me but you can't take her teddy bear and hang it above her reach" Tai said.
Yang then gave Ruby back her teddy bear and the baby reaper slowly stops crying.
"Now Yang, say that you're sorry" Tai said.
"I'm sorry Ruby for taking your teddy bear and making you cry" Yang apologetically told her baby sister and Ruby smiled and replied with baby gibberish.
"Now I think it's time for Ruby's nap time" Tai said as he carried little baby Ruby, wiped her tears and rocked her in his arms.
Baby Ruby slept peacefully in her father's arms with one hand on her teddy bear and sucking her thumb on the other hand.