Urgh… I hate it when I as a non-native English speaker have to educate native English speakers…
In this case, made even worse as the origin of the lack of understanding quite likely are non-native English speakers, like myself…

I am just going to be to the point:
The English term of Orphan comes from the Ancient Greek term of “Orphanos”(Ορφανός) meaning literally: “Those without parents”…
It is exactly the same what it means in the English language.

There is simply no words for those who have lost 1 parent, as it is not the same as losing both parents; A single parent is able to take care of his or her children, something that becomes an impossibility when a child has lost both parents.
I could also go into the terms like “fatherless” and how this has caused a problem with our understanding, and also give a history lesson about discrimination and that for a long time females were not regarded equal to males, but seriously, do I really need to do that?
If you are seriously not aware of that, you wouldn’t be reading this in the first place…

When we look more broadly at the misuse of these days, it has to do with people not being aware of other terms.
Like, children without parental care are often called orphan, even though “foundling” is the actual term.
A foundling being a child without known parents, most often because the parents abandoned him or her.
It is also actually a term where we find misuse, as people often use it incorrectly instead of “waif”, but that doesn’t matter as much as that term is hardly even used anymore.
And as I have explained too many times already, the directly linked term of “orphanage” is also incorrectly used.
The reason for that has mostly to do with the lack of understanding that children’s home and group home are not synonyms of each other, as the first one is “a place where children are cared for if their parents are dead or unable to take care of them”. (Thank you, Cambridge Dictionary)
While the latter one is a a place where people live together who are not of the same family, but do have something else in common…
Quite similar, but not the same.

Anyhow, as I could go on forever, and I start to feel like I am talking to a wall.
I am not native to the English language, and I am aware of this all.
Sure, it also took me a moment to learn it all, but if I can do it, why can’t those who are native to the English language?
I could also just have pointed to the fact that there are terms like “half orphan”, which kind of already should have said enough…