9 years, 6 months.
You first met Sophie when you were 8 months old and she was 7 months; back in 2011. We had just moved back to Nashville, and the two of you were in the same infant class at Kindercare.
Eventually Sophie moved away to Alabama (where we had just moved back from). Over the years, we have been able to meet up with Sophie a few times in passing.
However, I didn’t realize it had been 5 and a half years since we saw Sophie last! Back then, the two of you had just turned 4 years old.
That means that more time has passed since you saw each other, than how old you were when you last saw each other.
It’s funny how you have known each other your entire lives, but neither of you really remember each other; other than perhaps from 5 and a half years ago.
But this is the tradition now, at this point; that we will continually meet up with Sophie, in passing- and that will be the thing you two know each other from at this point!