What is the ruling on moving to live in a house that the family bought after an oath was sworn not to live in it, knowing that the one who swore the oath does not own a house, and he had sworn the oath believing it to be an oath of divorce?

The questioner's query is unclear, specifically whether he knows the exact wording of the oath or is unsure of its phrasing.

If the oath was by Allah, then it is permissible to live with the family, and an expiation for breaking an oath (kaffarat yamin) is required.

However, if it was an oath by divorce, then upon the fulfillment of the condition (living with the family), a divorce occurs according to the majority of scholars. Some scholars, however, hold the view that an expiation for breaking an oath is required, and divorce does not occur.

If the questioner has forgotten the exact words he uttered, the default presumption is the continuation of the marriage, and doubt is not taken into consideration. The wife remains under his marital bond, and he must offer an expiation for breaking an oath.