Note that “family” for income statistics means a household of two or more people who have relations from specified set between members, so that median family income is kind of like median household income, except that it excludes all single-member households as well as multimember non-family households (who are typically living together to save money), so it is biased strongly upward compared to similar household stats.
The census specifically doesn’t ask for income for children below 15, so perhaps that is the meaning of the sentence above, and per capita calculation does include kids as $0 income for calculating median - although that would be weird IMHO. Unclear, and I got bored looking for exact details, so gave up quickly!
Calling it $30k is wrong, but not very wrong.
Also note: “The U.S. Census Bureau also reports the median income for each family. In 2019, it was $86,011.”
(Note I didn’t double check numbers above, they were just the first I found from Google results).