Pesachim 49a compares a shidduch to a Talmid Chacham to grapes: "The mingling of the grapes of the vine with the grapes of the vine is beautiful and acceptable." It then contrasts this to a shidduch to an Am HaAretz, which it compares to the mingling of grapes and thorns - neither beautiful nor acceptable. What is the analogy of grapes? Are other fruit not pleasing and acceptable? (I'd like to clarify that I'm looking for an explanation of not only why grapes but also why not other fruit, such as olives to which Torah is compared.)
I think that the simple peshat is that if they are both virtuous, they are compared to two grapes; similar to the English idiom; two peas in a pod. Grapes would just be chosen since like peas they comprise a group of similar looking fruit.
Anecdotally, I found this idiom employed today, describing a male-female unit as "Like Two Grapes on a Vine".
However, R. Yitshak Yosef writes a different explanation as a derash in Yalkut Yosef. That grapes [differ from many other fruit in that they] require a preexisting support structure, to be supported, and the species does not stand on its own. So too, in a proper shiddukh, the bride and groom ought not stand independently, but rather, rely on the traditional behaviours of their ancestors.
ילקוט יוסף שובע שמחות א דרשות ענבי הגפן בענבי הגפן
מה שהמשילו ענין זיווג איש ואשה לענבי הגפן בענבי הגפן, היינו מפני שהגפן אינו עומד בפני עצמו, אלא נתמך תמיד על העצים שכבר קדמוהו...וזה הוא גם שבח לאיש ואשה כאשר מראש צורים אראנו ומגבעות אשורנו, שהם מיוסדים על דרכי אבות ואמהות שקדמום,
My Rebbe, the Stoliner Rosh Yeshivah shelitah, in Boropark, (R' Wolpin) told me an explanation of "why grapes" as opposed to other fruits.
All other fruits eventually rot with age. Wine is the exception. It gets better with age. So too a good marriage. If people build a home on the values of an Am HaAretz, then eventually, the superficial "love" will likely erode with time. As the couple grows, they tend to grow apart.
A home built upon the values of a daughter of a Torah scholar, will have virtues like patience, self sacrifice for one another , and higher values etc. These things will cause the couple to compromise and become one over time; until the marriage becomes wonderful like a fine wine...with age.
He uses this often when explaining the blessing to the couple.
A Pshat I thought of:
All fruit juice rot with age, wine is an exception, it actually gets better as it ages. The Gemorah teaches us that there is no final brick in a marriage, it should constantly be growing and progressing upwards, like wine. This is the comparison.
I’ve seen a beautiful parable regarding this point. Tomatoes grow green, they turn red only after they have already ripened and have grown to their full size. At this point, it can rot. A good marriage is one where the couple is constantly working on their marriage, for if they take a rest from growing, their marriage may begin to rot.
Every other fruit when turned into juice loses a level in the Bracha from Ha"eitz to Shehakol, However grapes when turned into juice / wine gets an upgrade in status from Ha"eitz to Hagafen.