He said "love" not "in love with". He did know there was a difference even if he struggled himself with the difference.

"So there is a goal. A reason to work together." Vader removed him hand but he didn't turn from her. "Leading in a war is not what I would have chosen for my children. It's brutal and damaging, and I can still tell you the name of every soldier I've lost. Those aren't burdens I wish on any of you."