Board Thread:Naruto Discussions/@comment-27090764-20151018105549/@comment-4912646-20151019044551

It had to have happened when Kimimaro was very young. Orochimaru took in Kimimaro, Kimimaro took in Jūgo, then Orochimaru developed the cursed seal and gave one to Anko. So unless Anko left Konoha with him like she did in that old filler arc, there is a very tight time span for all of this to happen.