Isaac was your older brother, Alex's best friend and consequently he was your enemy as well.

Isaac was staying at your place because Alex invited him over and you were annoyed. you opened your book and started reading.

after a few minutes you got up to use the bathroom. when you got back you saw Isaac sitting on your bed flipping through the pages of the book. he saw you, he started running which made you chase after him as he chuckled, running down the stairs to the living room.