"Older male cousin"... Cousin... No thanks. ^^; That's still too close a relative for me. ^^; He sounds too perfect, too, I kinda hope he stayed behind and took care of those little siblings of hers with his superior empathy and consideration.
Usually I like these romantic isekais to take the "destined to be together ever since who knows when"-route but now I'm really hoping the cousin-boyfriend is fully out of the picture. ^^; (If he turns out to be who I think he may be reborn as, I might mentally flip a table xD)