They do not impressive me. One of their Heritages gives them the Orc Iron Knuckle feat which gives them a lethal 1d6 fist attack. Seriously why could this not be a feat!?
I feel like the majority of natural weapons for ancestries are feat based, rather than being something you're stuck with on a character that wont use it.
It also gives a more flexible base for power and keeps it in line with other ancestries.
But yet this time it is not a feat which feels extremely weird, if it was a D8 fist I can see it being justified.
+str/+wis/+free/-cha. Triple stat with non-save flaw is always great.
10 hp, large, 25ft speed.
Level 1 feats:
Darkvision available.
Level 5:
Stance feat that lets you treat any non-reqch 2h weapon as having 10ft reach. Interesting but not worth the action tax. 1/2 level as fire or cold resist. Decent enough.
Level 9:
Flat DC 17 reaction to negate a physical damage crit. Fastball special also available at this level.
Level 13:
Teleport [speed] distance on a 10 minute CD
Level 17:
Huge size, all weapons have minimum 10ft reach, stance now gives +5 reach. Uncommon feat that grants interplanar teleport 2/week, self-target only.
There's more ofc but that's the stuff that jumped out at me. The only heritage that matters is the one that is a prereq for the reaction if you even want that.
I don't know how many feats for natural weapons there are but there's over 20 heritages that give unarmed attacks so there's plenty of precedent. Warrior Automaton for one example.
To answer the OP's original question:
Jotunborn were made by the gods to be the shapers of creation. After creation was finished the gods sent them to a subplane called the Fray. There they live a nomadic lifestyle following insectoid creatures called iivlars which produce silk. A few of them also pop back into Golarion whenever there's a natural disaster to fix creation.
Mechanically Jotunborn are a Large ancestry (with one heritage allowing you to be medium) with boosts to Strength, Wisdom, Free, and a Charisma flaw. They have the ability to glow with dim light thanks to the silk they weave into their skin. Not having the silk is the sign of being an outcast from jotunborn society. They have 5 heritages that generally have to do with the character's role in Jotunborn society (Warrior, Animal Keeper, Sage, Plane-Hopper, Weaver)
Their ancestry feats largely revolve around animal caretaking, creating things, grappling and being planar travelers. Plus the usual ancestral lore/weaponry feats
There were two feats that stood out to me. The first is a feat that's a copy of the Minotaur feat that gives reach as a stance. The other was Jotun's Boost, which lets you pick up a willing ally and toss them 25-30 feet (and strike as reaction) for two actions.
They have a feat to increase the reach of two-handed weapons.
Besides that, I feel they are mostly fine. They scratch the itch of a giant ancestry well enough so its a solid ancestry in my eyes.