Via letterbox.
[Beautifully handwritten, envelope wax sealed]
Dear Mr Black,
Your older self did mention that this might happen, but I admit that I didn't take the concern too seriously until now.
Are you now 14? I suppose then you won't remember me at all, but youhe you were were a good friend to me, although I haven't been here long at all.
Are you quite well? I know you are not an infant, but it can't be easy looking after both yourself and your nephew, so if you ever need a helping hand with anything you can count on me. As a friend, you understand.
I look forward to getting to know you better at this age.