This page of our guide to Greedfall contains a detailed description of Family Reunion companion quest commissioned by Vasco.
Where to start the quest?: Complete the previous quest of your companion and speak with him after some time, when you have completed one of the tasks of the main story.
Travel to Madame Morange in New Serene and interrogate her. Then go to Madame Cler and talk to her about Vasco's affairs. You can use charisma, intuition talent, or just pay 100 pieces of gold to get some information from the woman.
Move to the Hikmet Region and force Ferhat to confess his guilt. To do this, go downstairs and try to convince the employee to share information about their employer. Use charisma. Talk to Ferhat again and then head off to look for debt collectors. You can pay 200 gold pieces of debt, ask to pay later, attack them or use charisma. Killing a group is the worst option because you will get -1 reputation with the Congregation of Merchant.
Talk to Vasco about everything, and you will complete the quest. You will earn +4 reputation with Vasco and 1300 XP.