Most modern dictionaries define family relationships in a narrow sense. So that "son in law" refers to the husband of your daughter. However, I have encountered a very different use in the UK census of 1851. Extract 1851 UK Census

The 17 year-old son-in-law of Richard Holloway is not the husband of Sarah (or Elizabeth or Mary Anne) but the son of his wife Hannah (father unknown).

I would have expected either stepson or adopted son to be used to describe that relationship. But there is a certain logic to son-in-law, in that a male person not related by birth is being afforded the status of his son. Inheritance might have been a prickly issue but other documents suggest that there would not have been much property to disperse; and Philemon emigrated before Richard's death.

An ngram run on Google Books enables the relative frequency of the use of terms in published texts to be plotted through time. Although that tells us nothing about the meaning with which each is being used.

enter image description here

It is possible that this Census return was simply an isolated instance of the misuse of a term by an individual (either accidental or deliberate, to deflect attention from Philemon's illegitimacy) or it might reflect the more widespread use of a different meaning at that time.

It would be interesting to analyse a sample of documents from the 1851 census for similar cases, but evidence to confirm which meaning was meant would not be readily available. Are there other instances from this timeframe where relationship terms have been used in surprising ways?

Answer by Rob Hoare has provided confirmation that my interpretation is supported by others. Can anyone cite other examples that demonstrate this?

  • 2
    Interesting, I've never seen this before. I like the question. Commented Dec 7, 2012 at 2:05
  • 1
    I have also come across this in the 1851 Census and came on this site for clarification. Thanks all for your input
    – user2555
    Commented Oct 14, 2014 at 19:31
  • The same is true of the relationship of John Walker who is referred to as the "son-in-law" of Arthur Howland of Marshfield, Mass. Some people have falsely interpreted this to mean that Arthur's wife, Margaret, was the mother of Lydia Reed, the wife of Arthur's son, Arthur, Jr. However, the problem with this logic is that the reference appeared several years before Lydia and Arthur, Jr. were married. The better interpretation is that Margaret was previously married to a Mr. Walker who died soon after the son's birth and John Walker is actually the step-son of Arthur Howland, Sr.
    – user5454
    Commented Aug 23, 2016 at 17:30

6 Answers 6


The term "son-in-law" to mean stepson was quite widespread in the 19th Century.

I've come across it on many census entries, although stepson is the more common useage later in the century (or just plain "son", even if they have a different surname).

From UK Census Confusions:

In the censuses the term 'in-law' meant 'related by marriage' as it does today, however the key difference is that in the 19th century it was applied to children which is not the case now. A son whose mother re-marries would today be called a 'step-son', however he may be recorded on the census as 'son-in-law'.

Also in the US, from the Connecticut State Library:

Remember that meanings of words have changed over time. As examples, "brother" could once mean "brother-in-law"; "cousin" usually was a generic term for any relative; "son-in-law" could mean what we know today as "stepson"; "in-law", in the past could mean anyone related by marriage; "father-in-law" and "mother-in-law" could mean what we now know as step-parents.

Census indexes can be used to search for examples of this usage. On FindMyPast.co.uk, using the advanced search for the 1851 census, enter a last name, select son-in-law in relationship to head of household, and sort by age (youngest first).

If the surname is very common you may need to filter by county to avoid the search timing out.

Results are like this (name, birthyear, age, gender, birthplace):

SMITH, John         1844    7   M   Eton    Buckinghamshire     
SMITH, William J    1843    8   M   Aylesbury   Buckinghamshire  
SMITH, George   1841    10  M   Wycombe Buckinghamshire
SMITH, John         1841    10  M   Wycombe Buckinghamshire 
SMITH, William  1838    13  M   Wycombe Buckinghamshire 

Lots of young son-in-laws! Drilling down to the details you'll find most are not married. Following the wife back the children will usually have the surname of her first husband (or her maiden name, if she was not married when they were born). Daughters in Law are exactly the same.

Unfortunately the terms and conditions of Findmypast.co.uk don't allow me to reproduce any part their transcripts or images here, so I switched to Ancestry for the household containing the George Smith above:

enter image description here

In that family, it appears both the son-in-law and daughter-in-law are earlier children (and unmarried).

It would be interesting to see how many son-in-laws there are (under say 16 years old) in each of the censuses, but the search on Findmypast.co.uk isn't flexible enough for that (requires a last name or place, times out with too many results).

It's clear though that in 1851 it wasn't rare for son-in-law to be used as a term for stepson. There are 23 son-in-laws aged under 16 with a surname of "Smith" in Middlesex alone in 1851, compared to only 9 step-sons.

  • Upvoted both question and your answer because I've just found an instance of "daughter-in-law" in the 1871 Census for a 13-year-old girl: familysearch.org/pal:/MM9.1.1/V5RH-Z5Z and was about to ask the same question.
    – Jan Murphy
    Commented Jul 11, 2014 at 19:31

My understanding is that the term son, in law was to show that, insofar as it mattered legally, the son-of-the-wife had been truely recognised as his own son.

This was particularly relevant for (eg) inheritance purposes.

I suspect this is also related to the father-of-the-bride cliche: I'm not losing a daughter, but gaining a son - a seal of approval on the union.


I do find it typical and see the term used a lot, Where the children are from a previous marriage. Just today I received a Will in which a father John Clempson, puts his trust in his daughter Elizabeth to care for his Mother in law Mary Clempson..

Will of John Clempson 1808


The Quaker records for Nailsworth, Gloucestershire record the death in 1728 of John White, son-in-law of Charles Fowler of Woodchester and son of Elizabeth Fowler his wife. The poor lad was only 10 when he died. He was plainly what we today would call the stepson of Charles Fowler.

  • Hi, Peter - welcome to G&FH.SE! if the record in question is on a site which is not behind a paywall, such as FamilySearch, feel free to link it in here. You can add to your answer at any time by using the edit link under your answer. If you would like more information about how the site works, feel free to take the tour and look at the information in the help center.
    – Jan Murphy
    Commented Mar 22, 2016 at 17:55

According to the OED (Oxford English Dictionary), son-in-law also meant stepson as late as the 1730s. Consider that the OED usage patterns are estimates based on printed, often mainstream sources. I've found that in specialized contexts, usage can sometimes continue beyond what the OED reports. I would suspect that son-in-law may be used here simply in that older (now-obsolete) sense.


I will quote from an article I read in Internet Genealogy, a free magazine: "Those In-laws, in Eyes of the Law" (25 May 2023)

"Affinity is the legal term we use to refer to the connection between persons related through marriage but not common ancestry. We usually refer to them as in-laws, the people “in the eyes of the law” who establish kinship because of a marital union. These usually include the mothers- and fathers-in-law who are the parents of a spouse, brothers- and sisters-in-law who are the siblings of a spouse, and sons- or daughters-in-law who are the spouses of your own children."

"The latter term, however, was once used in another way and the reference to sons-in-law or daughters-in-law in court papers and other legal documents like property records and wills and testaments could cause confusion as to their intended relationship. In nineteenth-century records, the term sons- and daughters-in-law once referred to the children of a spouse from a previous relationship, as they were considered sons and daughters “in the eyes of the law” as a result of a marriage to their parent. Today we would refer to the prior children of a spouse as step-sons and step-daughters."

"It pays to bear in mind that descriptive and relational terms change over time and may not have the same meaning today as they did when they were recorded."

By Robbie Gorr, Internet Genealogy author

Not the answer you're looking for? Browse other questions tagged or ask your own question.