Alelou wrote:But in order to learn dancing from him, wouldn't you expect him to be older?
Normally, yeah, but common sense was killed in the Eugenics Wars, remember?
I did go and look, and though no, I don't find a mention of a sister in Breaking the Ice, it doesn't rule it out. Personally I took the first kid mentioned, Liam Brennan, as his nephew and ran with it from there -- different last name, so a sister's kid. It was just a guess.
Unfortunately, there is also some conflicting information in 3x01 (The Expanse, right?) where Phlox
specifically states that Trip has
one sibling or sister (I can't remember which, although I think he said "sibling"), a point that clearly conflicts with what Trip said himself back in "Fusion."
My solution for that in the Endeavour series was for Trip to have a major falling out with his family (instigated by his elder sister) that resulted in him changing his "next of kin" records to read that he had
only one sibling - Elizabeth - thus explaining why Phlox is wrong.
Yeah, its a crappy cheat, but the show is to blame since they had trouble keeping some of their internal continuity straight...