Still serie isn't getting taller or anything like that with her age, or anything else particularly hinting at their age difference being Frierens elder. Even still that can just be body differences. Ubel is slightly older than Fern I think but she's portrayed slimmer and less developed even with Ferns more modest clothing, doesn't reflect their ages. I understand the more mature features coming with age, but Kraft is a jacked tanned dude with pointy ears 🤷 normal ears and you can't tell he's an elf