If anyone thinks these parties liked each other before IK showed up, they weren't paying attention. They were each other's main opposition and competition in elections. Even as recently as the Senate Chairmanship election, they were at each others throat. The current PPP and PMLN accuse the government of using NAB and FIA to harass and imprison them, PMLN did the exact same thing to PPP in 2015. PPP openly backed calls for PMLN leadership to be thrown in jail following court cases towards the end of the last government, PMLN with the help of the security establishment moved to crackdown against PPP's militant wing in Karachi. PPP accuses PMLN of having a history of siding with the establishment to marginalise them (which is true IMO). PMLN was part of the whole trouble in 2011/12 that led to the dismissal of a sitting PPP PM. PPP returned the favour post-2013.
Back in 2008, PPP and PMLN made a coalition under the CoD, their reasons for sticking together were way greater than the current contention vs IK, that coalition was dysfunctional and it latest a few months - I think that's what will happen now at best, only differences is that today's coalition is guaranteed to be even more messy and unreliable. And not to go into ancient history, but these two parties were in way worse conflicts in the 1990s, much like government vs. opposition of today.
They don't trust each other, they're politicians who will be happy to undermine each other if it benefits them, and they'll return to this natural state once the current crisis is over. Whatever hopes they have of a coalition are wishful.
