Is this supposed to mean "youngest child"?
Not necessarily, if you coach a sports team, the last boy can be the one who arrived after the others.
Is this supposed to mean "last boyfriend"?
no, "my girl" is not "ma petite amie" and "my boy" is not "mon petit ami".
think of a sports coach talking about the last boy having joined the team.
in specific context, it could also be a mother pointing to her younger son.
Yeah, that's what I said too...
Why is "It is my latest boy" not correct? A translation of 'dernier' is 'latest'
What a depressing statement. I'm pretty sure I read those exact words in Game of Thrones somewhere.