Just wanted to add that the ability to freely name your sibling (first choice: "some other name") is a little confusing. The game automatically assumes that your sibling is female in the following section, even though the paragraphs leading up to that name choice only referred to them as they.
This means that, even if you give them a name commonly associated with boys, your sibling will still be referred to as she/her. It could be helpful to either continue referring to the sibling as they after naming them or to present the player with the option to choose between naming an amab/afab (assigned male/female at birth) child in the first place. However, that's just my two cents and I do realize that those ideas are probably not ideal.
Having said all this, I applaud the writers for adding a non-binary sibling. Normalize non-binary characters!