*Note: If your child falls between two Unders sizes, you may want to consider sizing up.
Unders by GroVia - Underwear (2 pack)
Both of my kids wear love to wear Grovia Unders as pajamas in the summer. My four year old daughter does not care for these as regular underwear under clothes - the cut is a little goofy when wearing leggings over them. My three year old son, however, has been wearing Unders since the potty training stage and prefers them over the standard boys underwear. They are super soft and comfortable. The only downside was because they don't have the tight elastic around the legs, they don't contain poopy accidents quite as well. But once we were beyond that stage (and even in it) they were the favorite underwear for him.
My daughter is extra sensitive to underwear. I loved grovia cloth diapers so decided to give these a shot and we are absolutely in love! Soft, stretchy, and tagless.