In the original (crap) iteration of Sonic Babies, Vanilla and Kevin were engaged. This time around, there's more meat to their backstory.

Up-and-coming fantasy author Kevin Azuka had been close friends with Vanilla Yamato, heiress to the Yamato Company, since childhood. It was around his teenage years that his feelings of friendship evolved into outright love, but he could never work up the gumption to tell her. Vanilla eventually married Ice Natsuyama, a man who cared more about Vanilla's wealth than for Vanilla herself. Ice walked out on Vanilla some eleven months after the wedding, leaving his ex with a baby on the way. Kevin finally confessed his love for Vanilla, blaming his shyness for being the reason she wound up in such a toxic marriage. Cream's birth was the final catalyst for their union, and they would eventually adopt an Adabatese boy named Sonic as their own son.