It is depend on the the culture, reldiuos and the education background of the society in which we live in and grow. what is marrage means in the particular society ? what is friendship means in a given society? what is the meaning of merrage in the relgious ofthat society ? so on are important.
Based on the a bove context, in ethiopia it is impossible to creat a friendship with the previous boyfriend or grilfriend after marrage.
white peoples may creat such friend ship.however they share all thing(including sexual intercourse) at the same time. if that is possible in our culture, it is also possible to creat such friend ship.