Yes — and there are enough examples that the “humans can reproduce with the wild/hairy people” motif is definitely real folklore, not something unique to Ostman or Ketil.
A few of the stronger ones are:
- Appalachian “Hairy Woman” / Yeahoh: folklorists collected several versions in Kentucky, Virginia and Maine. A human man lives with a very hairy cave-dwelling woman and they have a child; in some versions the child is literally hairy on one side and smooth-skinned on the other. citeturn580758search0
- Old Norse troll-women: this is actually a recurring saga motif, not just Ketil. A Cambridge study specifically identifies Örvar-Odds saga, Kjalnesinga saga, Hálfdanar saga Brönufóstra, and Ketils saga hængs as stories in which human men have sexual relationships with troll-women; in Örvar-Odds saga, the giant-maiden Hildigunnr bears the human hero a child. citeturn580758search3turn580758search6
- Zana of Abkhazia: this one is especially useful because she was a real 19th-century woman whom locals regarded as an Almasty/wild woman. She was described as huge, extremely strong, hairy, and without speech, and she had several children by local human men. Modern genome sequencing of Zana and her son showed she was genetically human, with ancestry closest to East African populations. So it’s a fascinating control case: the exact “wild hominin breeds with humans” narrative occurred around a real person, but DNA ultimately placed her inside Homo sapiens. citeturn859049search0turn859049search1
There are Pacific Northwest traditions in the same neighborhood too. Dzunukwa/Dzoonokwa, the Kwakwaka'wakw “Wild Woman of the Woods,” is traditionally portrayed as a huge hairy forest woman; one recorded tradition has her becoming the lover of a human man and producing a son. I’d treat the precise genealogy more cautiously because versions differ, but the human/wild-woman mating motif is there as well. citeturn294568search34
So Ketil and Ostman aren't isolated at all. There is a surprisingly widespread old motif of the human who crosses into the wilderness, lives or mates with a nonordinary hairy/wild person, and sometimes produces viable offspring.
And I found your Mount Shasta robot-grandma story.
You have two stories partly merged. The Mount Shasta boy was only about 3½ years old and was missing for roughly five hours, not several days. He disappeared from around Fowlers Campground near the McCloud River, and was eventually found alive under/near a bush. That core disappearance and recovery appears to have been reported locally. citeturn523228search2turn523228search9
The bizarre part reportedly came about three weeks later. He told his real grandmother, whom he called “Kappy/Cappy,” that he didn't like the “other Grandma Kappy.” According to the family account, this duplicate grandmother had taken him into a cave. He described old purses and guns, spiders/cobwebs, and other human-looking figures that didn't move. Light reflecting from the false grandmother made her look “like a robot.” She examined his abdomen and supposedly tried to get him to defecate onto sticky paper. Some versions include her telling him that he came from outer space and had been put into his mother's womb. Then she supposedly took him back outside and told him to remain under the bush until people found him. citeturn815808search5turn815808search7
That testimony comes from the family/grandmother and later Missing 411 circulation, not from a contemporaneous police interview with the child, so that distinction matters.
But I don't find a Bigfoot caretaker in that particular story.
I think the other memory you're blending into it is the Joseph Edwin Leffler case in Oregon in 1989. Joseph was three years old and genuinely disappeared near Estacada for two nights with three dogs. Contemporary reporting confirms that about 300 people searched for him and that he eventually emerged from the woods alive with the dogs; doctors believed the dogs probably helped keep him warm. citeturn163983search2turn163983search6
Later Bigfoot literature added a much stranger account: purported huge barefoot tracks, claims that a large humanoid carried or protected the boy, and that the boy said a “giant monster” fed him berries and looked after him. Those details come from Bigfoot researcher Thom Powell's The Locals and related Bigfoot sources, rather than the contemporary newspaper coverage. citeturn163983search1turn163983search3
So your memory appears to have combined:
Oregon lost boy → alleged hairy giant caretaker
with
Mount Shasta lost boy → duplicate/robot grandmother → cave → apparent specimen collection
And frankly, putting those two next to the folklore we've just been discussing gives us another very strange recurring theme:
wild/nonhuman humanoid encounters involving children, caves, protection or abduction, and beings that seem human enough to imitate or reproduce with us.
That doesn't establish what any of it represents, but we have definitely found more of the pattern than I expected when we started.