I will always see Purvi and Vishnu/Soham sharing a brother and sister relationship.
Just imagine, if you or anyone else was in Purvi's place, and you fall for Soham, and find out he's your brother? How awkward and disgusting is that?
(If Purvi's to accept Manav and Archana as her parents, and Tej and Ovi as her sisters when they aren't at all, so why would Soham be an exception?)
As for Arjun and Purvi to reunite- that will happen- Ekta's a master at breaking her well built jodi's and sending them on the road of judai and bringing them back together; plus, all these promotions of Arjun and Purvi, and flashbacks, and indirects from other shows and characters just tells you reunion will happen, possibly bot tomorrow but... soon .
Anyways, Soham and Purvi would cause such an uproar- whether people predict it or not, it'll be considered incest ... just saying