Some chains, and even airlines had family accounts. I know Hilton had one in the past. I think it's long dead, unless you were already signed up for it. I don't recall any US based airline having a family plan. British Air has one currently.

Only one person gets credit for a hotel stay. Hilton has a double dip program, where you get Hilton points and airline miles for each stay. If you're up for it, changing hotels everyday in the same hotel program usually gets you more total points, plus elite status more quickly.

See if your fiancé will make you an authorized user on the account with hotel credit card. Some hotels may not give you stay credit if someone else pays. Most, will probably be ok, though.