Is it normal i masturbate beside my sister

i am 23 yrs , i hv a sister of 27 yrs age,very beautiful.when i think of her, i become hot. earlier what i did, i masturbated thinking about her in my room alone. but since three months i enter her room when she is sleeping, and masturbate looking at her.,once when i was just reaching the orgasm she suddenly woke up, she saw me with penis in my hand the semen coming out. i directly left the room. i thought she will shout at me, or will tell to parents, but she didnt shouted neither discussed with me nor with the parents. after this incident i have also masturbated beside her. is it normal