Is my half-brothers half-brother related to me?

Question

[not using real names] Once upon a time, there was a couple named John and Melissa. They had a son named Bob, then divorced. Melissa went off and married George three years after the divorce, while John went off and married Kathy a year after the divorce. Melissa and George had two kids named Annie and Jack. John and Kathy had two kids named David and Hannah. Bob still goes to his dads to visit his half-siblings and dad every once in a while.

Are 'Annie' and 'David' related in any way, or is Bob the only one who is related to his own half-siblings?

Answer 1

Bob is the only one related to them. Annie and David are not related.

Answer 2

Not related, but if there is something going on Bob will be mad.

His sister dating his brother, does not sound good at all...