just being there is enough

It's simple pshat in the pesukim (Rashbam, Ibn Ezra), but it's a beautiful idea: the brothers returned home and told their father Yaakov that Yosef lived and was the viceroy over Egypt (45:26):

 וַיַּגִּ֨דוּ ל֜וֹ לֵאמֹ֗ר ע֚וֹד יוֹסֵ֣ף חַ֔י וְכִֽי־ה֥וּא מֹשֵׁ֖ל בְּכׇל־אֶ֣רֶץ מִצְרָ֑יִם

Two pesukim later, Yaakov himself exclaims that Yosef is alive and he must see him:

וַיֹּ֙אמֶר֙ יִשְׂרָאֵ֔ל רַ֛ב עוֹד־יוֹסֵ֥ף בְּנִ֖י חָ֑י

The brothers latched onto the fact that Yosef had risen to the height of power and was the head man in Egypt.  It's like telling someone that their long lost child has been found and he/she is a prominent doctor or lawyer or has a PhD and has won a Nobel prize.  

Yaakov, however, just says, "Od...B'NI chai."  My SON is alive.  What's important is not that he/she is a doctor or a lawyer or Indian chief.  What's important is simply that BNI, my child, is there.

What convinced Yaakov that it was Yosef was seeing the wagons that he sent.  Earlier this week I wrote about the gifts the nesi'im brought for chanukas hamishkan, which we read on chanukah.  Aside from their individual gifts, the nesiim also jointly donated 6 wagons and 12 oxen to pull them.  There is a Midrash (couldn't find it, but I saw it quoted in the Techeiles Mordechai) that says these are the wagons which Yaakov foresaw that caused him to believe Yosef was still alive.

Jealousy drove the brothers apart, but Yaakov foresaw that in the future the shevatim would jointly donate wagons and would also each individually give identical gifts so that no one sheivet gets singled out.  Yosef lived and was part of the family; the fracture between his sons would heal.