This question is asked a lot on Facebook by adoptees and nonadoptees for different reasons. The simple answer is whoever YOU feel belongs there as long as it’s historically accurate. If you have no interest in putting your biological family on there, there’s no reason you should. You can focus on the family you know and love.
Once you get started you will want to add siblings, but it is up to you if you want to add your twentieth cousin ten times removed. You can, but you certainly aren’t required. It’s up to you when to stop.
I personally like to add all spouses even if there are no children. I think part of that is because I wanted to honor the memory of my husband’s first wife and the daughter she was carrying. To me, they are part of our family.
I wish you the best of luck as you begin. Please like and comment on my posts so I know if you’re enjoying them.