Can a landlord break lease because of separating with wife and he needs a place to live, which the property is not in his name legally yet

No, he cannot "break" the lease simply because he now desires to live in the property.

ANY question on law needs to include your general locale as laws vary by area.

Some areas do allow a landlord to terminate a lease early if they or immediate family need to regain possession.

The property may be in the name of both himself and his spouses, but that gives him legal rights. Otherwise he wouldn't be the landlord.