Lionel Richie shared his thoughts on his daughter Sofia Richie's engagement to music executive Elliot Grainge, and he couldn't be more ecstatic.MORE: Sofia Richie's $300k engagement ring is mighty like father Lionel Richie'sSpeaking to American Idol red carpet, the musician initially joked: "It was a slippery slope there for a moment, as with all families."VIDEO: Lionel Richie performs All Night Long in New York throwbackHe then added: "I love Elliot, I've known him since he was 12, so it was one of those things where I don't have to go back and check out the kid, I know who he is. "They're so happy. As a papa, as a dad, that's my little girl.