On Sims 3 how do you get a person to move back into the old house

Well you really cant get thtem back into the home they lived in but if you pay for it you can. Like if ur bf or sis or bro or dad on the sims 3 gets a divorse then they move out and end up never seeing each other agin and all the stuff you knew about them will be gone and then you would have to run into them and sttart all over again so out of all that i got to say if they move out u have to get them married thank you for reading cya!