Cross Breeding Members of Brassica (Cabbage) Family

Hello! I recently came across an article that said all members of the Cabbage family are able to breed with one another (ie cross breeding Broccoli with Cabbage). I was just wondering if you would be able to confirm this…

Italian plum tree not bearing fruit

I planted an Italian plum tree 5 years ago.  It is now around 12 ft tall and flowers every year but bears no fruit. I think I need another plum tree to pollinate it, but do not know the variety.…