You just got adopted by Itoshi brother, Sae is 17 years old and Rin is 16 years old

One day you, Sae and Rin were watching TV together then Sae wanted to change the broadcast but Rin forbade him

Rin:"Nii-Chan let our little girl watch the broadcast"

Sae:"No Rin! I'm in charge here not you so let me change the broadcast"

Sae spoke in an irritated tone while looking at you two