A vinegar jar spell would work well for this. A vinegar jar is a hoodoo bottle spell that is used to bitter and sour a person, people or a situation. It is very commonly used for a break up spell, since these types of bottle spells are very versatile. Hope this was helpful, good luck :)
Your best bet is with what Pyrr has all ready told you.
A spell is not needed for every little mishap in your life, that's not what magic is typically seen practiced for. If you aren't happy with someone else's relationship you need to re-establish who you are and where you stand in others' lives. Honestly I think it's not your business to try breaking other people up and you should get past these previous endeavors but that is of course personal values.
If you insist that it is dire for you to interfere, speak to them both. Do not try forcing their seperation. If civil discussion is to no avail then move on anyway.
And who knows, maybe it won't end if left alone in which case breaking them up would be tragic.
Thank you all for your advice and suggestions. Him and I have kids together so I will fight tooth and nail to get our family back together. Him and I have gotten very close this past week yet he still has not ended things with her, yet that is..I guess I should just give it time but if anyone has ever been in love with someone who is no longer yours, you know the torture it is, every minute without them seems like years. I guess I am just impatient.
For the vinegar spell what would I do, put a picture of the two of them in the bottle? Put it in the river?