Although a historical document from pre-modern times mentions that Yoritsuna's father, Moritsuna, called himself Hei no Saemon no Jo Moritsuna NAGASAKI, assuming the surname of the Nagasaki clan, no such account is found in the documents from his times.
父盛綱が長崎平左衛門尉盛綱と長崎氏を称したことが近世の史料にあるが、同時代の史料にはそのような記述はない。