I don't think it's anything to do with parents, although of course people are bound to speculate.
If it's anything dodgy or that will lead to a court case, it will all come out eventually.
If it's personal or family-related, it's no-one else's business.
The important thing is that the head explains what measures are in place to cover for the absence, both in the short-term and in the longer-term if appropriate.
Won't stop all the gossip of course!