Everyone complains about Alt. Milla so I thought I wouldn't like her, (SPOILERS AHEAD) but I liked her to the end... Also, Elle's ENG voice actress did a FANTASTIC job with those scenes.
Ludger has a connection with the Key of Kresnik, is a descendant of Kresnik, and the chrono thingy. About Milla, that's easy, maybe. There was already a Maxwell in "prime" there cannot be two of the same spirit.. Alvin was close to both Ludger and the Key (Elle), maybe that's why?