Kenny Loggins wrote L&M's first hit, Danny's Song, in honor of his brother's newborn baby, when he was only a junior in high school.
Didn't know he wrote it that young ... a lot of emotional maturity in those lyrics. Loggins is an underrated musician all around, mostly because mainstream American tastes have moved so far away from the singer-songwriter genre.
Loggins tends to be thought of as the Footloose and Danger Zone-guy, which is unfair, really. He has dozens of great songs and, like you said, most of them are done in the singer-songwriter style and not in the over-produced style that his mid-eighties output would indicate.It's a lot like the Bee Gees. People think of them as that disco group, when in reality, they've had a twenty-five year career with only two or three of them being disco-oriented.

And I don't hold the BeeGees "disco" period against them anyway; they absolutely dominated the charts (esp. in '78) & deserved it.Kenny Loggins was also partly responsible for a #1 hit for the Doobies. Michael McDonald had part of a song (either verse or chrous, I forget), but was stuck. Loggins was invited over to dinner & as he walked up to McDonald's door, Mike was playing the part he had finished on his piano. Loggins asked about it when he got inside & MM said he was hung up & didn't know where to go. Loggins said he had a piece of a song that would go well with it and voila! "What A Fool Believes" was born.
Another Loggins hit,
This Is It, was written while his dad was sick and in the hospital. His dad was beginning to pity himself and was losing his will to fight his illness, Loggins had angry words with him at his bedside and went home. He returned the next day with his acoustic guitar and sang the song he had written the night before. His dad had an attitude turnaround and ended up being discharged from the hospital a few weeks later (where he was run over by a truck on his way out, ironically) {ok, that last part didn't happen}.The next time you hear
This Is It, check it out, it will change the way you hear it.