I ordered XS, S, and M.
I'm 5'3", 140lbs. Normally wear around a size 8. These pants are well made and comfy. Love the pockets for carrying my phone around the house. The waistbamd is very comfy and works with the drawstring, which is long and flat so you don't feel like a tight string is the only thing holding up your pants. The cuffed ankles helps for length adjustment. They were way too long for me, but since the ankles are like sweatpants, I can fold them up once and push them up.
The XS fit like slightly loose leggings. They were comfortable, even around the waist but, for pajamas I like a looser fit. They were just a Little too long, which is to be expected since I'm short.
The size Small was comfortable but still a little too snug for pajamas. The pink was also a little see through and made me look huge.
The size Medium was just a smidge too loose but very comfortable. Again, way too long, but as you can see in the photos, I can fold and push the legs up and they stay in place. The legs did not ride up while sleeping- which was the main purpose for the purchase.
I kept the size Medium and returned the other two.