@Clyde B Dalton-Vance
They will NOT be in your "Ancestral" Lines in "Family Tree" of 'FamlySearch'; as, they are "Living".
Does the Person have a 'FamilySearch' Account?
IF, they do; THEN, does the Person use "Family Tree" of 'FamilySearch'?
IF, they do, both, have a 'FamilySearch' Account; and, use "Family Tree" of 'FamilySearch'; THEN, you will, BOTH, have to have "All' the "Living" individuals/persons, in your respective "Private Spaces" of your respective 'FamilySearch' Accounts, that link/connect you together; as, "Duplicates"; BEFORE, you come to your FIRST "Common" DECEASED Ancestor.
IF, the "Living" individuals/persons are NOT, in your respective "Private Spaces" of your respective 'FamilySearch' Accounts; THEN, you will BOTH have to "Add" them to your respective 'FamilySearch' Accounts.
Sounds complicated ... but, it is NOT.
Let me explain ...
[ And, please bear with me ... I am very 'verbose ... that is my style ... ]
We do not have our OWN "Tree" in "Family Tree" of 'FamilySearch'.
We ONLY have "Branches" (ie. Ancestral" lines), 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 'On-Line' "Websites" (eg. "Ancestry_com"; or "MyHeritage_com"; or, the like); and/or, 'standalone' personal (computer) programmes (eg, the OLD, now no longer supported, "PAF"; or, "Ancestral Quest"; or, the like).
We DO NOT have "Private"/"Personal" 'Trees' in "Family Tree" of 'FamilySearch' like other 'On-Line' "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" individual/person 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(s)/Patron(s).
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?
I cannot see my spouse and in-laws in Family Tree
Can my living relatives share a Family Tree private space to work together?
How does Family Tree protect the privacy of living people?
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.
ps: Related 'Question' (post) ...
In Ancestry DNA this has happened to me many times.
Here are some strategies I've found helpful.
(Long story short I found a "stray" from a north of England tree. He had moved south and married one of my
ancestral cousins. His researcher relatives had been ready to give up on our DNA connection after two comment
exchanges but for some unknown reason I was determined to search further. End result - they were delighted).
I always ensure the DNA connection is aware of Family Search Family Tree. I'm rather amazed at how often someone I am assisting already has ancestors in Family Tree. An experienced researcher, now retired, I sometimes offer to mentor my new "cousin" in developing their research skills.
Success has included a connection with as little as 6cm with only four people on their tree. There are others with closer connections with which I've not yet had success.
Hope this helps.
LegacyUser: There are several things that I do to determine a DNA matches connection to me. First, if they have a small tree with at least a few people that are viewable. I will make a shadow/research tree. By building out their tree it may allow you see that connection. Secondly, I make sure my tree that is connected to my DNA test has as many branches as possible. Sometimes our DNA matches are not coming from our direct line but from those offshoot lines such Aunts and Uncles. By fully researching these lines and including them in your tree matches will appear with the connections as long as the DNA match's tree is correct. Thirdly, then there are those DNA matches I have that come from slavery. I administer kits for my mother and her remaining siblings as well as my siblings. There are DNA matches of European descendant I have no idea how they are connected to my maternal line. I have some idea which side of my maternal line but not which ancestor they directly connect to. That is something I am still working through. Some of these DNA matches ancestors have proximity to my ancestors in where they lived and others do not. It is a slow process but one I hope to conquer one of these days. Searching for our ancestors is much like the story of the Tortoise and Hare. Slow and study wins the race.