Details: Karen was a student for Andy's at college and despite the age gap they started dating and started a serious relationship. But when Andy was deported Karen realized her feelings for Keith and ended their relationship as well as Andy wanted children whereas Karen didn't. After Keith's death the two recoiled and together raised Karen and Keith's daughter Lily.
Details: Andy was in a relationship with Karen before Lily was born and due to the death of Keith. Years later Karen and Andy recoiled and decided to travel the world together on a yacht and during this time Lily and Andy formed a father-daughter relationship and share the bond of one being extremely close although both admit that they miss Keith/would give anything to have him back.
Details: When Andy and Karen first started dating Lucas wasn't keen on their relationship wanting her to be with Keith but following his death. And the couple recoiling and Andy helping to raise Lily the two grow closer and Lucas as able to confide in Andy.