The first time was when I heard my friend in college tell his dad he loved him at the end of a phone call. My dad has said it to me maybe three times in my life.
Real eye-opener was in therapy when I realized I never felt true love or even support or compassion from them. Cutting them off was easy because I was never made to feel like I was allowed to need help from either of my parents after the age of maybe twelve.
I wish I could empathize with how my wife feels about missing her dad (he died very young). I'm as supportive and helpful as I can be, but I have no strong feelings about the idea of never seeing my parents again.