You can't compare the 2-term rule to the demand that family members of past presidents should be disqualified from running as candidates in the presidential election. Every US citizen must be eligible to participate in the POTUS election. You can't discriminate someone by saying that your husband or brother was previously the POTUS.
Yes, you can. That was standard policy in many large corporations a few decades ago. At IBM in the 70's, if a male employee happened to meet its future wife among his colleagues, it was standard practice that she would have to leave the company before the 2 would be allowed to marry. That's close to the idea I'm defending here. Besides, I think the world has seen enough of Hilary and the Bush family.