Just a matter of when you're comfortable with it. SILs (DHs sister) partner isn't referred to as uncle by us but she refers to him as uncle. They've been together for 2 years but I just don't feel right about it. On the other hand it's become evident that some of my family have a problem with the kids calling DH uncle. The kids don't care though and still refer to him as uncle. We've been together for 12 years. My sister's bfs have never been referred to as uncle. Despite all 3 being long term there just wasn't that level of comfort with any of them.
Sent from my pho....oh who am I kidding. It's rarely used as a phone