Conversation so far:
What was Basel?
Holbein bought a house in Basel, in St Johanns-Vorstadt.
What did he use the house for?
He presumably returned home to preserve his citizenship, since he had been granted only a two-year leave of absence.
What was significant about the house?
Enriched by his success in England, Holbein bought a second house in the city in 1531.
What other things happened during this period?
During this period in Basel, he painted The Artist's Family.

Question: What was significant about that painting?
Self-contained rewrite: What was significant about the painting of Hans Holbein the Younger?