When you say 'Tree', are you referring your "Pedigree" View, in "Family Tree" of 'FamilySearch'.
IF, so; THEN, they will NOT, unless you "Change" to the relent "Spouse" (where there there is more than one spouse).
They will appear on the various "Person/Details" page/screen for the various individuals/persons, just not in your DIRECT "Pedigree" View, unless you "Change" to the relent "Spouse" (where there there is more than one spouse).
I hope this helps.
In both the portrait and landscape (is this what you mean by "pedigree"?) views of my family tree, the person does not show (just an "add child" box), nor does she appear on our common parent's person page.
It DOES NOT matter WHAT "Pedigree" View you are looking at/viewing ...
In whichever case, you need to "Change" to the relent "Spouse" ...
[ where there there is more than one spouse ].
Are you referring to, the "Printed" version, of a "Pedigree", of an individual/person?
IF, so, THEN, you need to "Change" the "Preferred" Parents; BEFORE, selecting "Print".
As an aside ...
In any case ...
You and your "Half-Sibling" NEED to be, CHILDREN, with the SAME Parents, for this all to work.
You can BOTH be Children with MORE than ONE "Couple" (ie. set of Parents) ...
It is just that your "Relationship" to the various Parents will be DIFFERENT ...
[ eg. Biological; Adoptive, Step; Foster; Guardianship ]
Here are some "Knowledge Articles" in 'FamilySearch':
How do I add step, adopted, and foster parents to a child in Family Tree?
How do I add step, adopted, and foster children to parents in Family Tree?
How do I specify biological, step, adopted, and foster relationships in Family Tree?
Thanks. I just sent you a private message.