In Sonic Wings 3, Sonic Wings Special, and Sonic Wings Limited, the Russian twins Chaika and Pooshika fight in order to earn money for their father's medicine. However, their father is only shown in Special and Limited.
The girls' father is ill with an unnamed malady, and their primary concern is getting his medicine to him. However, in one ending in Special and Limited, the girls return home to find their father perfectly healthy. He reveals that he just had a hangover, and the twins hit him with one of their giant Russian dolls. (This ending occurs after the boss battle with Balbi in Special and Osaru in Limited.)
Strangely, the twins' father is identical in appearance to Mao Mao's manager. This is likely because the game makers simply used the same image for the two very minor characters. Video System's website says that they look alike "for some reason" and raises the question of whether they are the same person.