Turned on by sister

When i was 10 years old my older sister emma was 14 (4 years olda than me) and from when she was 14 i had a crush on her i dont get turned on by girls but for some reason i got turned on by my sister. in my family it was a case of that my parents were away alot so is only me & sis in the house.
We were so open that sometimes she would jus walk around our house naked.One night i was feeling very horney in purticular and because our beds were facing each other when i saw her lieing down facing me reading a magazine.
I pulled back the covers and started masturating calling out'Emma ,emma lets be lezbiens together please i love it when u walk around he house naked it makes me wet'
she quickly looked over (i was doing this with my eyes closed)so i left one eye half open and continued.
Then i heard her say 'shan are you awake' i jus started sreaming in joy emma continued speaking 'shan wake up'
i quickly opened both of my eyes and pulled back my covers and looked her like nothing happened she quickly asked me 'do u get turned on by me'as she pushed out her 36D boobs.
'I Just noded and started at her boobs in amazment
she said 'well lets be lezi's ' she stripped naked and lay on her back and said 'y dont u climb into my bed with me so i did
she was finering me it felt wonderful so then she said 'its your go she said lick me in my fanny' i felt soooooooo horny it was hard to say no. started licking her and then she said that i licked her enough 10 minutes later.
Now my big sister is 23 and i am 19 is it normal that i still get turned on by her?