Introduction
In the general concept of kabbalistic soul mates, we marry the other half of our soul (may we all be zoche to find our true zivug and have a bayit ne'eman b'yisrael). Our goal is to become one, like we once were. The point is brought down in, for example, chassidic mamarim based on the kabbalah that "back to back" oneness is not as sublime and lofty as "face to face" oneness, so having been split apart, we can turn and face each other and reach a new level of eternal oneness. Judaism, it seems, is the most truly romantic of the belief systems of the world, placing the closeness and true yichud (intimacy) between couples as the highest pinnacle of creation, the upper echelon of spirituality, and the entire Torah is practically a guide on how a husband and wife can learn to become closer than is humanly possible. Their reward is (at least in part), the eternal oneness that is the reward of this effort.
[Yes, this question will not likely be interesting unless you have a little romance in your heart.]
This question is more specific than the title implies, please read the background carefully:
Sources and Background
In this question I am considering just the case where one spouse from a successful, loving marriage dies younger, and therefore the remaining spouse remarries (which is encouraged in Judaism: Tav le'metav tan du mi-le'matav armelo). Let's bring some opinions about what this means for the eternity of the couple where the husband dies first (most of the opinions deal with this, there are a few brought for the other way around towards the end). This is the stronger case because generally speaking, the wife is the "centre", the "crown"1, the "home"2, and thus it makes more sense to ask this question from the husband's point of view (imo).
According to Hagahot Yad Sha'ul3, a woman will reunite with her second husband after the resurrection. See also the Chatam Sofer (355) who ruled that when a woman remarries after being widowed, her second marriage, in effect, nullifies the bond that she had with her first husband4.
The above opinions come up in the context where the woman had children only with the first husband. In the case she had children with both, the Kabbalah says that she will be reunited with her first husband in Heaven5.
There is also the opinion in Piskey Teshuva 124 that brings that a woman will be reunited with her first husband, unless the second marriage was more distinctly successful (according to Rav Aviner's understanding). In Yabia Omer 7:40, Rav Ovadia paskins that a woman should be buried next to her first husband, unless she specifically requests otherwise.
The differences between the above opinions is sometimes framed in the context of whether the wife was a virgin at the time of her first marriage. This also raises questions about what if the woman did teshuva, or if she converted prior to getting married, and I'd be happy if someone brought up answers to that in their answer if possible.
With regards to the husband, there are strong sources that claim he is always connected to his first wife6. See also the discrepancy on the duration to which a husband must wait before remarrying vs a wife7.
There is much more to discuss. If anyone has "The Philosophical Quest" by J. David Bleich, I believe a lot of information on this topic is found there around page 300 onwards.
Question
The question is, how do we solve this complicated problem, and what are the ramifications? If we hold that the wife is reunited with her first husband, what of the second husband (if it was his first marriage, and even if not)? Or vice versa. What if there were several remarriages, such as with the Chatam Sofer, lo aleinu?
A sad image of a young man, madly in love with his wife, lying on his tragic deathbed, knowing that his wife will no longer be his, never again, she will remarry and be someone else's for eternity comes to mind. Is he being punished? What greater Divine gift can a man lose than his home, his crown, his soul mate? Maybe he will pray that her next marriage won't be successful so he can keep her. A worry that perhaps one shouldn't fully let one's heart fall for one's spouse, just in case, comes to mind, especially if he is her second husband. I think it's an important question... The tremendous task of becoming one with someone certainly won't benefit if there are doubts in this area.
How can we have a more optimistic, as well as complete and sensible picture of this whole issue, that maintains the strongest Jewish opinions on "soul mates"? If it's unavoidable that some of us will be "alone forever" chas veshalom, then what will be our solace?
It's an emotional question, I'd appreciate answers that:
a) Support the strongest Jewish stances on "soul mates"
b) Are based on deeper insights, such as sourced in kabbalah and chassidus
c) Are hopefully optimistic! Becoming "One" is such a profoundly important idea, I'd rather find answers that make it ikar, rather than dilute it in any way.
E.g. a "nice" solution might be that when a spouse is lost, a part of the living spouse "dies with them", and they truly are united forever. A quick study of Shaar Gilgulim would yield that such things are certainly not out of the realm of possibility, and would be beautiful, yet a positively identified source is sought here.
1 - Mishlei 12:4
2 - Rashi on Shemot 19:3
3 - YD 366:3; See also She'arim Metzuyanim B'halacha 199:7; B'tzel Hachachma 2:73
4 - See also Be’er Heitev, EH 17:1; Pitchei Teshuva, EH 17:1. See also Knesset Hagedola, EH 17:2; Birkei Yosef, EH 17:1 and Emunot V’deiot 7:6, Birkei Yosef, EH 17:1; Chatam Sofer, Nidda 70b, contrast with the fact Rav Chananya ben Chachinai didn't remarry after his wife died and was resurrected in Ketubot 62b, and commentaries there, and Mishne Halachot 9:402 regarding relations after the death/resurrections of Har Sinai.
5 - See Zera Emet, YD 146, which also explains how a husband prefers to be buried next to the same woman that he had his first children with. See also Yabia Omer 7:40.
6 - Based on Keren Ora, Yevamot 55b, and Tosfot, Bava Batra 114b
7 - YD 392:2; Be'er Heitev 392:2; Aruch Hashulchan, YD 392:4,5