From personal experience I can say that whether the mother works (for pay, doesn’t necassarily matter if she works outside the home or from home — which can actually be worse) has a greater effect on how much attention kids get or if they need to be surrogate mothers than the number of kids she has. And being from a large family does NOT make the child feel like he/she is just a number. Kids are usually at different ages (except multiples) are of both genders with totally different natures, aptitutes, and very often looks to be treated like a pack. And every half decent parent is well aware of their child’s “Malos” and “chasronos” and makes decisions accordingly (simple example: is he ready for summer camp?). There are issues of jealousy etc. to contend with, but kids develop good lifetime coping skills from the challenges they overcome. This whole “surrogate mother” issue is complicated as many older kids actually adore their siblings and prefer to “mother” them. Everything in moderation and dependent on the child’s age, but you can’t set blanket rules.
Also, kids that were “spoiled” growing up, regardless of family size, very often resent the fact that they were given too little responsibilities and are thus not equipped to handle life, especially their own family. Final point: I don’t see any “burned out kids” from helping at home, am I really that oblivious?