Technically, both forms are correct. But, as you already figured out, multiple possessive apostrophes in a row is awkward. I could see myself using the phrase verbally and informally, but I wouldn't use it in written English. I'd probably use "The motorbike that belongs to Jane's brother is..." This kind of thing can even be confusing to native speakers.

Thank you to all of you.

The Pearson book is correct. I can't think of any context in which I would say "the motorbike of Jane's brother"

Both are correct, but the first one is more common, in my experience.

Both are correct, but the second sounds awkward and unnatural. We would generally avoid this construction.