Butterick 6296 is a useful basic pattern for loose-fitting women's pyjamas. I have made the top but preferred to use another favourite pattern (Kwik Sew 3602) for the pants. My fabric is Lantana, a blend of cotton and wool by Liberty of London in a design called Clarisse and purchased on British eBay.
The fit is generous. Instructions for adding the sleeve bands are awkward compared with other patterns. Following those of Burda 2691 would be an improvement.