Which of the following is a valid form of proof for family size documentation?

A marriage certificate is indeed a valid form of proof for family size documentation because it provides official recognition of a legal union between individuals, which contributes to establishing family size. This document often includes the names of both spouses and can indicate a familial relationship, thereby helping to verify the existence of a household unit.

In the context of family size documentation, other options may not directly provide information about the number of family members. For instance, employment records primarily relate to individual employment status rather than family composition. Tax returns typically show financial information and may include dependents but are not as direct in providing proof of the immediate household members like a marriage certificate. Utility bills indicate services provided to a specific address but do not specifically identify the individuals living at that address. Therefore, the marriage certificate stands out as a clear and direct form of documentation for family size.