I would continue monitoring the situation and intervene as little as
required. My own mob consists of Spot, the boss cat, his brother Nacho, and
their mother, Sammy. My tabby female Cassie is approaching 7 yrs old. The
two brothers are 2 yrs old and their mom is 3 yrs old.
Spot has asserted his dominance over Nacho. Sammy likewise has installed
herself as Alpha female. All goes well most of the time.
I only intervene when things get particularly ugly. To do so at other times
only seems to cause an escalation of bad behavior, as the one attempting
display of dominance will sometimes ramp up his efforts to make up for
whatever I may have undone by intervention.
Nacho will sometimes attempt to renegotiate Alpha male status with Spot.
Spot at first seems rather passive. When his threshold of tolerance is
reached, he will take Nacho to the floor, biting him on the scruff of the
neck and pin him. Upon release a few good swats are delivered to send him on
his way. These things are fairly easy to distinguish from ordinary play
wrestling and common interest in the same toys. The vocalizations of pecking
order dispute is unmistakable.

The real problem is when Nacho goes after Cassie. Cassie normally submits
and flees the room. If Nacho goes after her, Cassie can be counted on to let
go with the most blood curdling screeches of pain even though Nacho hasn't
physically done ANYTHING to her. I think Cassie counts on that as my cue to
jump in and get the big oaf away from her. These two are the most likely to
engage in a high speed, leaping and diving, furniture busting pursuit. Their
collisions with stationary objects are legendary in the neighborhood and
have produced a few limps and wincing headaches. I try to stop this sort of
thing cold, as it seems to be more common bullying for amusement, rather
than legit social order purposes. It also shows the most potential for
injury. Nacho isn't particularly graceful and really doesn't seem to give a
sh.t what happens when he decides to rampage.

Then there are times when the entire red cat clan decides to harass Cassie.
They stalk her and take turns chasing her and covering possible escape
routes to a point that the old girl is definitely stressed out. Just like
kids, there comes a time when play crosses the line.