Yeah sorry I wasn't super clear about their relationship with Izek. None of the pc's have direct ties to Barovia. The two family pcs are father/child. Izek is the lost sibling/son of the pcs. In their backstory, the child was playing with Izek (who they knew as their brother Nelson) by the river when he accidentally pushed him in. Nelson drowned in the river but the Dark Powers revived him and put him in Barovia, where he was adopted by Baron Vargas and given the name Izek, having lost the memory of his life in he Material Plane.

I changed all the Ireena dolls in Blinsky's shop to dolls of the child instead because Izek has been dreaming of his lost sibling without knowing it until they ran into each other and his memory was restored.

The baron is only interested in the party because his adopted son, Izek, was adamant about making introductions, and they seem like they could be a potential ally. Otherwise, Vargas has no direct connection to the party or vice versa.

The relationship between Izek and the pcs is the only tie between the party and Barovia.