Cannot become soulmates

My sims have maxed their relationship and friendship bars, are married, are best friends, and still cannot become soulmates (which is needed to complete the soulmates aspiration). I don’t use cheats or mods because I like collecting achievements so there is literally nothing I can do at this point. Tried googling a bunch of stuff to see if there’s a workaround, and apparently this bug is almost 6 years old now.