What does Doyle mean?
Anglicized from Irish O Dubhghaill, from 'dubh' meaning 'dark, black' and 'gall' meaning 'stranger, foreigner' — 'dark foreigner', a term historically applied to Viking settlers.
What does Sullivan mean?
Anglicized from Irish O Suilleabhain, from 'suil' meaning 'eye' plus a second element usually read as 'dubh' (dark/black), giving 'dark-eyed'. The second element is disputed; alternative readings give 'one-eyed' or 'hawk-eyed', so the 'dark' sense is probable rather than certain.