Do stay-at-home parents and single-income families need a bigger cash cushion?

Generally yes, because a single-income household has no second paycheck to fall back on if that income stops, which raises the stakes of any disruption. Aim toward the higher end of the range, often six to twelve months of essential expenses, and pair it with adequate life and disability insurance on the earner, since the fund alone cannot replace a career's worth of income. It also helps to keep the stay-at-home partner financially involved and able to access accounts, so a crisis does not leave them locked out. Consider whether the non-earning partner could return to work if needed, which affects how long the fund must bridge. A larger buffer buys the whole household time to adjust without panic if the sole income is interrupted.