Just a thought; is it possible that Serrin was actually older than Dart, in terms of years lived when they recognized? It's a pretty longwinded chain-of-thoughts, but I'll try to break it down:
- Dart is an infant during the Madcoil Attack, which took place seven(?) years before EQ1. The main part of OQ takes place seven years after EQ1 (making Dart 14)
- SaBM takes place three years after OQ (Dart is 17)
- Venka is born during SaBM (making her 17 years younger than Dart)
- Venka is still fairly young when Kahvi leaves during KoBW, she does tell Rayek that "The Wolfriders finished by upbringing", Probably less than 100-years-old (Dart's age is Venka's+17)
- Let's assume Kahvi and Tyldak when directly to the Go-Back lodge after leaving the Thorny Mountain holt, not much travel time from there to Sorrow's End either (especially with the eagels)
- Judging by Bethia's condition Serrin is probably born very soon after HY#2
- The 'Go-Back Attack' seems to take place about a year after Kahvi's initial raid...
- Dart goes into wrapstuff not long after the attack (while Serrin is still a young child)
- The narration says that "a very long time" passes before Serrin, who's all grown up and has a lifemate, cuts Dart out of the wrapstuff. "A very long time." To me that could easily be 500 years. Or even 1000! Serrin and Talmah could've been lifemates for centuries when this little 'developement' occurs...