Taking just the initial question posted, not reference to the criminal case:
My DH and I started "going out" at 15. We were most definitely "in a relationship".
I'm not referring to a sexual relationship I'm referring to a deep emotional bond.
Any one would saw us together had no doubt about it. We waited until we were in our twenties to get married but the fact that we were together (with no break ups) was not surprising to our family or friends.
I understand that some teenage romances are over in a few weeks or months but it's not true to suggest that just because someone is young they aren't capable of real love.
My DH and I have been together for nearly 30 years, nearly 20 of them as husband and wife.
At 16 and 17 we were definitely considered a couple by everyone, parents, friends and school.
Oh and btw at 15 we did " go out" of course we did cinema, bowling, cycling, hill walking, for meals etc. Why wouldn't we?