Can the word 'erroneous' be used to apply to a person, as in the term 'erroneous spouses'?
Tl;dr: erroneous is now rarely applied to people; use "mistaken" unless you have a good reason. The brave may continue reading.
The OED finds the only uses of erroneous not obsolete or archaic are applied to "doctrines, opinions, and statements," where the word means mistaken. The sense of "morally faulty" is marked "Obs. or arch." but has the virtue of Lord Byron's use in Don Juan in 1819:
Haidée and Juan were not married, but
The fault was theirs, not mine; it is not fair,
Chaste reader, then, in any way to put
The blame on me, unless you wish they were;
Then if you 'd have them wedded, please to shut
The book which treats of this erroneous pair,
Before the consequences grow too awful;
'T is dangerous to read of loves unlawful.
In a separate sense of misguided (and equally unused), the OED quotes Sir Thomas More from 1829:
He who shows himself grievously erroneous upon one important point must look to have his opinions properly distrusted upon others.
A more modern source, the 2005 novel Little Fugue by Robert Anderson describes passengers on a delayed train
good-naturedly swapping stories about getting lost amid the London miasma, entering the wrong flat, and sleeping with the erroneous spouse.
"The Mister's had the sack over me head for twenty-five years anyhow." a charwoman's voice joked from the economy seating.
Here the word is humorously applied to the spouse mistaken for, not the spouse making the mistake.
In a more serious vein, from 1977, The Journal of Libertarian Studies:
The erroneous person allows a whole host of fleeting temptations to divert himself from his own true goals.
The google reveals that the term "erroneous spouse" is almost a term of art on online genealogical sites to describe an ancestry tree that wrongly records a marriage.