The number is part of the parent, not a sibling, because <br> is self closing.
It isn't obvious to me how to isolate those numbers. If you know that there is a number for each title, and if the numbers are sequential, then you can do it by counting them, but I suspect there are too many 'if's involved. You might be able to do it by getting the text of the parent and counting lines.
What does the parent html block look like?