Help!!! My brother is down as his wife started contacting her Ex

Good evening all! Please i need mature replies on this topic. My elder brother is really hurting right now.

The Story.
My elder brother got married earlier this year…before the marriage, he was fully aware that his childhood friend[Michael] had dated his wife to be with sexx involved. The wife is the truthful type and lays everything bare. Michael is well aware that his ex [my elder Bros wife] is fully married to his friend[my brother]….My brothers wife and Michael recently reconnected again on social media and has since started up chats that “MAY” lead to them flirting. She shows my brother the chats and gives him every update. My brother is not happy with this development and is yet to communicate this to his wife.

1…Should he tell the wife to block of Michael (his wife’s ex, whom is coincidentally his childhood till date friend) ?is this a wise move considering the fact that this might make his wife start hiding stuffs
… The wife is cool with maintaining contact with this particular ex[Michael]….thought he tells my brother everything /the chats.
2….Can you allow ur spouse still in contacts with his/her ex?
3….Should my brother just talk to Michael straight up to stop chatting his wife?

By Miss Nora