I mentioned this before to you lol. Half-siblings are still very much related. Yeah, if, say a half-brother and half-sister have a child, there's less chance to have a child with deformities or issues, but there's still a higher chance. They still share half the DNA from one parent. Which makes them 100% related. It's not like step-siblings, where they are only related by marriage and have no blood relation.
So just imagine that your own father or your own mother had a child with another woman or man. Would you not consider them properly related to you just because the child doesn't have both the same father and mother as you?