All of my Mark/Ate songs come from the musical Assassins, and none of them are romantic, they just all make me think of Mark and Ate.
The Ballad of Booth and Unworthy of Your Love... as sung by Glibt XD! Those are the two that really do it. Though, I won't lie, I vaguely imagine them hooking up every time a Republican president is taken out >.>
(why, yes, I am in a Mark/Ate mood lately)
Jesse and Laura had this amazingly normal and romantic courtship pre Jesse telling her everything, so for them I give The Glasgow Love Theme, and will stray away from my Confederate Rock playlist.