Are you talking about a "Deceased" individual/person; OR, a "Living" individual/person.
Or, are you talking about an individual/person who has recently died/passed away; where, you have them as "Deceased"; but, your Child still has them as "Living"?
We all have DIFFERENT (in fact, UNIQUE) 'FamilySearch Person Identifiers' (PIDs) for "Living" individuals/persons in the "Private Spaces" of OUR 'Personal' "FamilySearch" Accounts.
When a "Living" individual/person dies/passes away, we separately change their 'Status' to "Deceased", which means that they come out of our "Private Spaces" and can be seen by all Users/Patrons.
Thus, quite often, in those circumstances, the recently "Deceased" individual/person can, in fact, be in two (x2) states in "Family Tree" at the same time - both, as "Deceased" in some Users/Patrons "FamilySearch" Account; and, as STILL "Living" in other Users/Patrons "FamilySearch" Account.
It can take some time to get ALL the "Duplicates" of recently "Deceased" individuals/persons in the many "Private Spaces" in the many linked/connected "FamilySearch" Account to the 'Status' to "Deceased".
And, eventually, ALL the ALL the "Duplicates" of recently "Deceased" individuals/persons WILL need to be "Merged" / "Combined".
If it is something different than the above situation, let us know.
And, we will see if we can assist you.
I hope this helps.
when you say "my child's family tree"
do you mean the family tree that your child see's when THEY logon with their account ??
if so they will need to fix it (especially if it is for a living person)