How can I be related to someone but not their parents?
It sounds like there are several sets of parents, such as biological, foster, adoptive, etc. Depending on which parents are selected as preferred, you could well have that situation.
Another possibility is that the person is 15 generations from you, meaning that the parents are beyond the scope of the "view relationship" function.
What tool are you using to find the relationship?
If you are relying on the relationship calculator on FamilySearch, it is only as good as the information contributed to the tree. If there is a flaw in the logic, or if a family is connected inaccurately, then the relationship calculator can't determine the correct path.
The calculator also takes only the simplest most direct path. Because my maternal family comes from the rural southern US, we have a large number of multiple relationships and pedigree collapse. The calculator cannot handle complex relationships.
I've found that a spouse of a relative (a cousin of any sort) is related, but their parents will not show a relationship. I have a related question.
If I have done all of the ordinances for the spouse of a cousin, except the sealing to their parents and I don't want to do their parents' work because of the indirect relationship, what should I do with the "Sealing to Parents" ordinance?
@Leah Dempsey, please ask your question in the Temple category. If you're using the website, you can do so by clicking "Temple" in the Categories box in the right-hand column here, and then clicking the big blue "Ask a Question" button.
(In my world, "sealing" involves a sealant.)