you can do boolprop testingcheatsenabled true then shiftclick on the mailbox and hit set pregnancy relations with....
or u could just do boolprop testingcheatsenabled true and then
shift click on ur sim and click "spwan" and click more, and then click sim modder.and then click relationships and click... the sims name and click love. then click the other sims name and click love.
P.s. (me to other) and the other one says (other to me) 💛