On Goobues and Timelines.

[Rannie]

I'm not sure about Thancred's exact age though as it was more Gridania's 1.0 story I was taking notice of, so Professor Moose or one of the other 1.0 loremasters would be better to answer this question as they're much more knowledgable on the subject than me.

https://www.finalfantasyxiv.com/anni...?rgn=eu&lng=en

Perpetually passing by, Thancred had drifted in and out of Minfilia's life for years. He had been seventeen when they first met—five years her senior. Or so he claimed . His carefree demeanor believed many secrets, not least his skill with a blade. The manner in which he had battled the creature which slew her father was proof of that. Of course, he preferred a subtler approach when circumstances allowed.

Atleast 17 when he met Ascillia/Minfillia

which makes him atleast 27 in 1.0 and atleast 32 in ARR

so since he was "Sharlayan" due to Louisoix's timely retrieval of the Thancred as a kid in Limsa when he tried to relieve the poor Elezen man of his money pouch.... yeah the lady's man was an adult. With 16 being the age of adulthood there.

Recent graduates of the Studium, the twins were now sixteen summers old─old enough to be considered of age in Sharlayan society. And so, although he opposed his children's planned journey, Fourchenault had not sought to bar their way.

https://www.finalfantasyxiv.com/anni...?rgn=eu&lng=en