My son is adopted by my second husband and I would like that relationship to show.
Add the information for your living son if not already added.
Copy your son's ID # into your computer clipboard. (short term storage)
"Add child" using copied ID# in your detail page with Famil Members of you and your 2nd husband as couple.
Edit your son's relationship (small box with pencil) and add Relationship type "Adoptive" to your 2nd husband. Your relationship type with your son should remain Biological.
This allows your son (with same ID#) to appear as "Adoptive" with 2nd husband and biological with your 1st husband.
Note: because you are dealing with living people (Privacy) only you as the account holder will see this in your tree. No one else will see this.