u/La_Villanelle_

We see hints of this with Aemma and Rhaenyra. Rhaenyra brought Baelon a dragon egg from Dreamfyre clutch, had already chosen the name Visenya for the baby before she even knew he was a boy, and was genuinely offended when Daemon took the egg she had specifically saved for her little brother. I really think that if Baelon had lived, Rhaenyra would have cared for him deeply and probably would have been a very loving older sister.

As for her half-siblings, I don’t think she was ever really given much of a chance to form that kind of relationship with them either. Show-wise, I honestly understand why she would distance herself from Alicent and her children after everything that happened between them. Alicent was her former best friend, married her father, and their friendship completely fell apart. I would probably still be angry and uncomfortable too. Even then, there was a deleted scene where Rhaenyra actually tried to interact with Aegon and get him to say her name, which at least shows that there was an attempt at some point.

After Rhaenyra and Alicent’s relationship completely deteriorated, though, I think having a normal sibling relationship with Alicent’s children became nearly impossible in both the book and the show. Book-wise, Alicent was already openly feuding with Rhaenyra when Rhaenyra was around ten and Aegon was only two. Those children were basically raised in the middle of that hostility from the beginning. Show-wise, Aegon and Helaena are still very young when Rhaenyra is preparing to marry and have children of her own.

So I don’t really see Rhaenyra’s distant relationship with her half-siblings as proof that she would have been a bad older sister. The circumstances surrounding those relationships were poisoned before any of them really had the chance to develop naturally. Baelon probably would have been the best indication of what Rhaenyra could have been like as an older sibling if she had actually been given that opportunity.