Avoid shooting people/groups from close distance with any WA lens which can capture 74 degrees horizonal Angle of View and wider...avoid 15mm on APS-C or 24mm on FF camera....inducing perspective distortion by shooting with too close of a subject distance! About 18mm on APS-C and 28mm on FF is relatively safe from induced perspective distortion.
Ragged Ann and Andy are identically sized. Ann's head photographs twice as large as Andy's head, although he is a mere 24" behind Ann. Imagine that Andy is like the legendary skinny Jack Sprat, and Ann was his very ample wife...HER girth would be exaggerated even more, when compared to her skinny husband. Ann would take up 4X the area of Andy, so if Ample Wife is already 2X larger in girth than her skinny husband, in the photo she would occupy 8X the volume as her husband...NOT a way to make her pleased with the photo!
Ann''s right hand is significantly larger than her left hand...body parts closer to lens are exaggerated more than parts farther away. Imagine Jack Sprat's wife's ample bosom exaggerated in size even more by its proximity to your UWA lens, much to her dismay. Yet only about 15" separates her two hands.
This is why UWA is a dangerous FL category to shoot any people unless you are very careful about induced perspective distortion, such as what is exhibited in the above photo.
The near hand is 'bigger' than the far hand, the near person is 'bigger' than the far person, so shooting a large group at an oblique angle is more 'dangerous' for induced perspective distortion with too WA than a longer FL, and why the back row of a group appears smaller than the front row.