The wild life of having siblings

Kim Yeri also known as Miss Katy Kim is the big sister of three younger ones. Their names are Kim Yoorim a year younger, Kim YeEun who is nine years younger, and the youngest Kim ChaeEun who is 12 years younger. When you think living with with is crazy, try thinking of Kim Hanbyul, Kim Hanbin's younger sister and also older cousin to Yeri who she has to baby-sit orders by B.I's mother. At first Yeri thinks this is crazy, but she learns that nine year old Hanbyul acts just like her two younger sisters so she says sure.

B.I on the other hand has no clue what his mother has asked and finds out though his boyfriend Bobby and learns that Red Velvet's 20 year old maknae is baby-sitting his baby sister. Hes fine with it...until Hanbyul has more of a liking towards Yeri than him...her big brother. Of course jealousy runs through his veins but what gets him more is that not only does Hanbyul have a liking towards Yeri, but also to Seventen's 20 year old Maknae Dino and NCT's Mark and Lucas. The case of big brother blues comes over B.I.

How can He do prove to B.I oppa that his Younger sister still loves her big brother even if she does have a liking towards other idols?