Hi! I have a vcf file, comprising real data on populations evolution (not sure about what species)

There are 2 scenarious about how this populations evolved (with or without migration). Basicly it's a two steps scheme:

1. An initial population splits into 2 subpopulations - A, B
2. A subpopulation B splits into 2 subpopulations: B_1, B_2

the only difference between 2 scenarious is the presence of migration between A and B_2 So my goal is to model this 2 scenarios and find out which is more close to the real data (vcf file)

Whats the best way to do it?