Feeling Resentful of My Younger Sister's Musical Potential

i am a former gifted kid. i was extremely intelligent, and, more relevantly, i was really good at music. now, i’m sure you can guess, i’m an extremely neurodivergent (adhd + autism) and mentally ill, burnt out adult. my parents were very young when i was born, and verging on old when my siblings were born, so despite being an adult, i currently have 3 siblings who are 11, 9, and 2. the 9 year old has adhd as well, and recently she’s enjoyed playing with a keyboard toy that the 2 year old got for xmas. music has always been a major thing on my dads side of the family, grandmother used to play sax, grandfather used to play piano and was a music teacher, dad was forced into piano and cello, then found love for guitar and punk rock and was in a band for ages. i sang from a young age, had drum lessons for about 2 years when i was 9 or 10 ish, my dad taught me some guitar, i then taught myself the ukulele, got a major music scholarship at my school, and then had guitar, piano and singing lessons. i used to be encouraged about how quickly i picked things up, multiple teachers have told me what a bright future i could have in various types of music, and basically music was what i was known for. now, the relevance is this. my grandfather over the weekend apparently noticed some musical potential in my sister, i think she figured out how to play some basic melody to a nursery rhyme or something, and he has decided to pay for her to have some sort of music lesson. i feel awful about it but i find myself resenting my sister for it. i can’t make myself believe that she might actually be good at music because that was MY thing. I want the music lessons. I want to be given all the praise again. but as i mentioned earlier, im now a very mentally ill and burnt out adult, which means i very rarely do music anymore, and when i do, i don’t tend to share it. i want to get back into it so badly but alas the brain says no. what i want to know (if you’ve read this far) is this: am i being a grade A asshole? obviously i’ve said nothing other than advice about where to start, and supportive stuff to anyone, but im really really struggling with it. i think this is the closest i’ve come in ages to being actually musically motivated, but it’s for awful reasons. it’s just purely because i feel a deep seated need to compete with her and prove that im better than her, which is AWFUL because she’s literally 9 years old, and i’ve had years of practice over her! am i just being a proper dickhead who needs to get over themself? like there’s a very small part of my who’s happy to have something to share with her but the overwhelming majority of me is just praying that this is a short lived hyperfixation of hers and that after a few weeks of lessons she gets bored and moves on, which is, again, awful of me. am i right in hating myself for this? is it awful if i get back into music again now just because she is? i genuinely want advice, be harsh if you must. do i need to just get over myself or is this in any way reasonable?