Its a matter of complex privacy / identity theft issues and even legal issues.
FamilySearch is working on ways around the privacy and legal reasons.
but the solution has to be a pretty tight solution.
I for one don't want my private info being passed around to others.
For the most part the info I add for living person in my account - is for my purposes and my purposes only.
FS really was designed for keeping track of info on deceased persons - not the living. - though it does allow you to add info to the living for your own purposes - but the info belongs to you only. passing it around could end up leaving FamilySearch liable.
How can you avoid duplicating living relatives if you don't know if someone else has added them?
if they are living persons - then you should not worry
you should only worry about duplicating deceased persons.
living persons you enter are for your info only - they are not considered duplicates - because they only belong to YOU and cannot be shared with anyone else.
As Dennis said, don't worry about duplicating living individuals, it isn't an issue currently. That said, consider why you are entering them into the Family Tree system. If you are logging everyone you find..maybe you don't need to spend that much effort in that way. If you are keeping data on all of your descendants or descendants of your parents...do you need to if they are members of the church, since the church keeps membership records on everyone? Are you adding living people so that you can add Memories to them? While those memories may not be easily found right now, once those folks have died and the Living record that you have created is marked deceased, all of those memories you may have attached will show up attached to that record.
Further to what 'Dennis' and 'Anne' have already proffered ...
Regarding your original 'Question' ... How can you avoid duplicating living relatives.
Short Answer: You CANNOT
'Yes', we are creating "Living" DUPLICATES.
And, in many cases, a number of times over ...
That said ...
In this case, that is OK, acceptable; as, there is NO other choice ...
I know it sounds wrong ...
But, let me try and explain ...
We do not have our OWN "Tree" in "Family Tree" of 'FamilySearch'.
We ONLY have "Branches", that are interconnected, in this SINGLE "One" World "Tree", for all of us, that is "Family Tree" of 'FamilySearch'.
"Family Tree" of "FamilySearch" is NOT like Other "Websites" (eg. "Ancestry_com"; or, "MyHeritage_com"; or, the like); and/or, 'standalone' personal (computer) programmes (eg. the "Old" no longer supported "PAF"; or, "Ancestral Quest"; or the like).
We DO NOT have "Private"/"Personal" 'Trees' in "Family Tree" of 'FamilySearch' like Other "Websites"; and/or, 'standalone' personal (computer) programmes.
We do not even, own; or, manage; and, are NOT even responsible for, the "Deceased" individuals/persons in "Family Tree" of 'FamilySearch'.
"Family Tree" of 'FamilySearch' is built on a "Open Edit" Platform - hence, why any registered User/Patron can "Edit" (ie. Add, Delete; and/or, Change) ANY "Deceased" individual/person in "Family Tree" of 'FamilySearch'.
You can certainly "Merge"/"Combine" any "Deceased" individual/person in "Family Tree" of 'FamilySearch' with another "Deceased" individual/person in "Family Tree" of 'FamilySearch', regardless of who the User/Patron was that initially created those "Deceased" individuals/persons; as, they DO NOT reside with the User/Patron who initially created them - they are "Public".
If fact, you can ONLY see "Deceased" individuals/persons in "Family Tree" of 'FamilySearch'; except, with this 'rider', that you can ALSO only see "Living" individuals/persons in "Family Tree" of 'FamilySearch' that YOU created; as, they reside in your "Private Spaces".
No other User/Patron can see ANY "Living" individuals/persons that were created by another User/Patron; as, they ONLY reside in the "Private Spaces" of the User/Patron who created them.
We CANNOT even see the ACTUAL Record in "Family Tree" of 'FamilySearch' of our IMMEDIATE Family (eg. Spouse; Children; Parents; Siblings; ETC; Etc; etc) if they are "Living"; and, they have their own 'FamilySearch' Account.
Of course, you can create your "Living" Family members; and, record them in "Family Tree" of 'FamilySearch'; but, they will ONLY be seen by you:
- You cannot "Share" them with any other User/Patron.
- You cannot "Merge"/'Combine" them with any other "Living" individual/person residing in the "Private Spaces" of another User//Patron.
There is CURRENTLY no mechanism in "Family Tree" of 'FamilySearch' for Users/Patrons, to "Share"; or, "give permission" to "Share", the "Living" individuals/persons in their own "Private Spaces" with/between other/another User/Patron.
There are a myriad of "Privacy" Laws within the many various Countries and Unions throughout the World - it is a nightmare to negotiate.
"Family Tree" of 'FamilySearch' is used in many Countries and Unions throughout the World; and, as such, must adhere to the myriad of "Privacy" Laws throughout the World.
Hence, "Privacy" is one of the reasons that we cannot "Share" the "Living" individuals/persons in our own "Private Spaces" - it is NOT the ONLY reason; but, certainly has a bearing on the matter.
Another factor is that such would have to be 'Coded'/'Programmed' into the Programme that is "Family Tree" of 'FamilySearch'.
'Yes', these "Living" individuals/person in "Family Tree" of 'FamilySearch' WILL, in fact, in many (most) cases will be "Duplicated" - unfortunately a necessary situation that currently cannot be avoided.
I know that there are "Duplicates" of the "Living" ME - at least, one for my Wife and each of our Children, not to mention my other ("Living") extended Family members.
Here are some "Knowledge Articles" in 'FamilySearch' in regard to "Private Spaces" and "Living" individuals/persons:
What is a private space in Family Tree?
Who can see my living relatives in Family Tree?
Here is a good place to start, with how things work in "Family Tree" of 'FamilySearch' (and, other programmes as well):
Introducing The Family History Guide
The Family History Guide
I hope this helps.
"How can you avoid duplicating living relatives"?
By not entering them. Very simple.
Data about living people doesn't belong online. Data breaches of various sorts are inevitable this age of cloud computing, but no data breach can reveal information that isn't there.
If you need a profile for a living relative in order to connect to a branch of deceased relatives, create a placeholder or bookmark profile, with just enough information for you to know who it is. Non-names like "mom's sis" are perfectly fine for this purpose.
Use an offline family tree program (saved and backed up to local disks, not the cloud) for keeping track of living relatives. There are many options, free or reasonably-priced, and several of them can synchronize with FamilySearch.