The biographies that I tend to work on follow a chronological story line.
After you describe the death date/place, you could indent an excerpt of the person's obit or otherwise describe it. Then cite the source.
Alternatively, if the obit is a source for the person's family members you could have a == Family == section under which you could write
Her obituary identified the following family members:<ref>Cite the obituary...</ref>
(then list the family members).
Or if you're not comfortable adding the actual names of the family members to the bio itself; you could simply say "See Jane Doe's obituary for more information about family members." (and link to the obit.)