how to make a network with just string

I have data like this

Tera1   Bestman
Tera2       Bestman
Tera3       Bestman
Tera4       Bestman
Tera5       Bestman
Brownie1    Tetra
Brownie2    Tetra
Brownie3    Tetra
Brownie4    Tetra
Brownie5    Tetra
Brownie6    Tetra
Brownie7    Tetra
Bestman     Tetra

I want to make two networks. so all the tera1 to 5 are linked to Bestman (it gets a bigger ball) then all the brownie 1 to 7 link to Tetra (get a way bigger ball)

something like this

I am not sure how to make it happen in R. I was thinking to give a weight to the members like this

memebers    Core    value
Tera1       Bestman  1
Tera2       Bestman  1
Tera3       Bestman  1
Tera4       Bestman  1
Tera5       Be开发者_StackOverflow中文版stman  1
Brownie1    Tetra    2
Brownie2    Tetra    2
Brownie3    Tetra    2
Brownie4    Tetra    2
Brownie5    Tetra    2
Brownie6    Tetra    2
Brownie7    Tetra    2
Bestman     Tetra    3

This way there are 3 clusters , 1 all link to Bestman 2 all link to Tetra and 3 is connection between bestman and Tetra