Vrashek spent some time adventuring in Darokin before travelling to Karameikos. Vrashek and his companions at the time could have done some adventuring with Cassi & Mikel at that point.
How about this...
... the group had been known as the Swords of Darokin, but they had no objection to Cassi and Mikel joining their number. Indeed, for three years the band of adventurers had included as many arcanists as blades. No one had said an ill word to the young couple when they left to marry and start a business and a family; in fact, the surviving Swords at the time had all been there when Cassi and Mikel exchanged vows before the Twelve Watchers in Darokin City.