Here's the baseline but I haven't went into detailed brief CS with them yet, so they might change with time:

♂Ren: Olive skinned serious and boyish features. Copper hair and usually dressed in a simple tunic, breeches, boots and belt. Sky blue eyes and seems like there’s usually fleck of white floating in them. 

♂Aarem: think Harry Potter’s Prof. Snap in looks, only with a slight wave to his dark hair. 

♀Xiah: every shifting appearance of a pretty woman so she could be rather flexible and no form which is model/superstar/etc, pretty is off limits to her though she tends to add some trait that is above normal. Like mother of pearl colored irises, blue black hair, etc. 

♀Duuri - wild red hair and pale, sickly looking sick and bright green eyes, very thin and weak looking yet energetic. She almost looks to be around a 16 year old girl and the youngest.