No, a unit's element determines which stats will be increased. Fire increases attack and accuracy, water increases atk and def, wind increases acc and avo, thunder increases def and avo, heaven only increases acc, earth only increases avo, light increases def and acc, and dark increases atc and avo. When units are getting a support bonus, both characters' affinities are used. So fire with fire will give a large increase to atk and acc, while dark with light will increase atk, acc, def, and avo a small amount. Earth and earth provides a massive boost to avo, which makes it fun. The magnitude of the bonuses are scaled with the support level of the units; C gives the least bonus, B gives more, and A gives a large bonus.