Responses
There are no half siblings here, only two twin sisters, and the blue hair dude is NOT related to the mc either by blood or by upbringing (he only shares some years of "upbringing" with the mc's sister -- NOT with the mc herself -- because he lived a few years under the same roof as another foster kid of the sister's adoptive dad, but he wasn't even officially adopted by the dad, so he was at most her sister's co-foster kid: barely even her sister's foster brother)
Sooo, at first I was okay with them too, I could feel that they were feelings but now that they are brother and sisters I am like who is her half sibling mother I have so much questions...