Can a divorced couple remarry?

Yes, sims can remarry as often as they want. If you don't want to use MC, you will have to go the normal route: romantic interest (woohoo doesn't trigger that btw), going steady, propose, marry. You can do that within a single conversation. Make sure you get them to "extremely irresistible" through the usual romantic interactions, or none of those options will show up.

It may be good to tell the other woman to "just be friends" though, if you don't want any further surprises.

Sometimes, simply quitting and reloading the game helps to get missing options back. Also, the first option you should look for is "go steady".

Yes, your Sims can be remarried. No, he doesn't have to break up with his romantic interest for that to happen but it would be better for his marriage if he did. Breaking up face to face is better than text (if you can manage it).

How does Rita appear in his relationship bar? Does she have the empty heart with the red 'x' on it? If so, have them do basic interactions until the option 'Ask to Be Friends' appears. This will remove the 'ex' symbol and give them a 'clean slate' (so-to speak).

From there, have them spend time together doing all the interactions and things they like to do together (whatever that is). Rita will eventually forgive him and they will move forwards and towards marriage again.

The 'Ask to Be Friends' comes up in either the 'Friendly' or 'Mean' category (and I think it is under 'Mean' for some reason). Personally, I wouldn't move Tom out because he then becomes a townie and will have free reign to pursue (or marry) whomever he wants (or the game wants to puts him with). I suggest keeping him under your control until the block which keeps him and Rita apart can be removed. Just my opinion.

: ) I'm sorry this is late Rhiannon58 hopefully it got solved, but if not I have luck with what mw1525 said to do:

First have them do a few Friendly category thing (not romantic),
Then go to the Mean category and 'ask to be just friends' will be there.
Only then will the wedding ring with the red X in it disappear.
Once that happens, you can start with the romantic things to get to Propose.

Hi!! Yes, of course, your sims can remarry if they want to.

@meme009 - That is one way to do it. But it's not the only way, as the players above have explained.

@Avatarit - Thanks. I knew I saw it both places! This explains why.

@Rhiannon58 - Was this issue ever resolved? Are your Sims happily re-married?

Thank you all for your help. I had to take a break from TS3 because my game was broken but the amazing team here helped me fix it today. I used the friendly interactions until I got the "let's just be friends". That cleared the X for marriage. Then I did the romantic interactions and the beloved Hanks family is once again whole!

Thank you for your help today @igazor! Truly. I've been wanting to play again but dreading the frustration. My game is fix, the Hanks are once again in love so the world is all right now! I've had a fabulous day getting to know my Sims again!