I know a couple of people (women) who seem to have gotten into the habit of referring to children who aren't theirs as 'theirs'.
For example, one of them refers to her stepchild as 'hers' if people asks about them, another looks after her close friend's children and frequently has pictures of them on fb, comments on the pictures referring to the kids as 'hers'.
I get that they have a great relationship with these children, and that is fantastic but AIBU to think that maybe it is a bit U to refer to children who aren't yours as 'yours'? It just feels a little bit disrespectful to their mothers, who they live with and are their main caregivers? Or am I just a killjoy 
I just know that, personally, anyone referred to my kids as 'theirs' I'd be pretty pissed off.