Is Sister Princess: Re Pure hentai?
No
Rated PG-13 (Teens 13 or older) on MyAnimeList and not tagged as Hentai.

TV · 2002 · 13 episodes · PG-13 - Teens 13 or older
Drama, Harem, Romance
After a long time, Wataru has decided to leave his family home and live on his own. The girls have also decided to split up and most of them are living separately as well. But none of them have forgotten about their brother and still stick together to meet him. (Source: AniDB)
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