If he’s a live in he qualifies as parent status in my book...a baby gets killed and you’re worried about the use of the word ‘parents’...sheesh.
The word “parent” means more than shacking up with a chick who just happens to have kids. For all I know this guy was a stand up dude who committed one negligent act, but the usual 32 year old male shacking up with a 23 year old who has two small children is not a parent in any sense of the word other than (possibly) a biological one.