There are two ways to look at that.
If there is no case, then of course there is no recusal. Recusal proceeeds on a case-by-case analysis. If "the case" is a piece of hallucinated fiction, there is no case, and any recusal is in effect, meaningless. Just for example, session has to recuse from a case where his wife is charged with a federal civil rights crime.
But make no question, Sessions has to recuse from a case that involves his wife. He also has to recuse from a case that involves the Trump campaign.
There is no case. What are the charges? There are none. Jeff is under no blind obligation to recuse for any frivolous yet-to-be-named not even criminal allegations being hurled at his wife, and the relationship with his wife is not the same as his relationship with Trump. C’mon.
Also, Jeff’s wife is not the president. The guy with the power to pardon is immune from criminal charges. What he is not immune from are political charges which require no facts, just suggestion and innuendo which is all a special counsel would need to bring for theoretical criminal charges that could never go to court. If Trump even allowed it to go to court, which he never would, the supreme court would throw it out. The only purpose of this nonsense is just to serve as a pretext for impeachment.