I think this is a very cultural thing. When I interview candidates at my current job, we are interested in hearing about their life outside of work, since we want to know how we can best collaborate
If they have to pick up their kids in the afternoon, then it's probably better that they work closer with the other parents than of they're late risers who prefer coming to the office at 10
I don't know where are you from or where do you work, but this sounds like a big "no-no" in an interview setting if you are based in Europe.
It's totally something you can bring up later, when already hired, if the job description made clear that it gives you flexible working hours.
What if the team they're interviewing for doesn't has any parents. I think probably it is fine to ask about their life/interests outside of work. But if the interviewee isn't comfortable answering those it is better not to push
An employer making career-affecting decisions for their employees based on whether they have kids or not sounds like a great way to get sued.
That said, I have been asked if I had kids, in an interview. Later in my career, when I was trained to perform interviews, I was explicitly told to NEEEEEVER ask that. And if the candidate volunteers it, to basically pretend you didn't hear it.
This sounds more like post-hiring admin, unless you're discriminating against parents?
If the interviewer was fishing around for information for when I start work or if I have kids, the only thing that'd come to mind is whether they're trying to frame me as a slacker to disqualify me from the interview process.
Maybe the above is an European thing.