Discovered the requirements to get all 5 members to join Tavia
Vince - You must shoot Danny and leave with Justin. Reason is when Tavia offers him to join Justin would have betrayed Vince which leads to his loss of trust to strangers.
Wyatt - You must win the Rock, Paper, Scissors and leave Eddie behind
Russell - You must trust Nate so Russell can trust Tavia when she offers the invite in 400 days even if you find Nate a AO
Bonnie - You must tell the truth to Leland so he can go with Bonnie. If Leland does not leave with Bonnie she will not join Tavia because she lacks the ability to trust anyone.
Shel - The two possible ways are that if you kill Stephanie, Tavia must mention there are other children in the settlement. If you did not kill Stephanie and run away she and her sister will automatically join Tavia from fear that Roman is still hunting them.