See
this article for information about how to record a spouse or child whose name is unknown.
But note that you must also have
a date and place of at least one event in their life in order to clear the ordinances for temple work.
In addition you must
have permission to perform ordinances for a non-relative for anyone born in the last 110 years. As indicated in the linked article if you don't believe there are any living relatives, you may have to provide proof of that.
And, finally, you can't do any work for the spouse or child if it is possible they are still living. Unless you have evidence of their death, you can't assume they are dead until
at least 110 years after their birth or 95 years after their marriage.
Overall, your best source of information is the Help Center on familysearch.org and contacting Family Search support.