ryanair.com operates a seasonal weekly service starting from March 16th 2013.
In the interim, your best bet would probably be to fly ryanair.com or aerlingus.com to Malaga, get the Cercania(Train) from Malaga Airport to Malaga Train Station and then train or bus to Seville.
There are regular train departures throughout the day taking between two to three and a half hours.
See: www.renfe.es
There is also a daily bus leaving Malaga Airport for Seville Plaza das Armas
at 16:45 arriving 20:00. One could also get buses from Malaga several times a day to Sevilla.
See: alsa.es
