@WeBuiltThisBuffetOnSausageRoll
I have to disagree with that.
For the Craig Douglas one, there is a line 'She was too young to fall in love and I was too young to know'. Clearly teens around the same age and all about first love.
For the Union Gap song, to me, it is a clear acknowledgement that, although he seems to love the girl, he knows the age gap is too much and that pursuing it will lead to heartache. From memory, the song doesn't mention age. Bit like me, in my 50s, lusting after one of the student nurses. Yeah, might happen but I could never keep up with a 21 year old and I know it. The song is a very similar theme to Abba and 'Does your mother know' but I have never heard of anyone questioning the motives of Benny and Bjorn.
What do you think of 'Little Children' by Billy J. Kramer? A male of undetermined age offering money and sweet to said little children and asking them to keep a secret.
Some people might say that seeing things in songs the way you describe is just a mirror of your own mind.