Shinseki-no-ko-to-o-tomari-dakara

I’m not sure what you mean by "shinseki-no-ko-to-o-tomari-dakara." I’ll assume you want a complete article explaining and exploring the Japanese phrase "親戚の子ことを泊まりだから" or a similar phrasing about "staying over because of a relative's child" (or "親戚の子を泊める／泊まる") — I’ll produce a clear, complete article about the cultural context, grammar, etiquette, and examples for the phrase meaning "having/hosting a relative's child stay over." If you meant something else (a song, title, or different wording), tell me the exact Japanese and I’ll adjust.