[On the joining of a believer’s descendants to him]

Answer (and Allah is the One who grants success): This question contains several questions, and these are the answers arranged according to the order in the question:
1- The righteous descendants will be joined to their righteous forebear of high rank. But this does not mean that the descendants will be joined to their forebear such that they are in his very rank and station with Allah—so that the believer from the Household (Peace be Upon Them) would be in the station of the Prophet (May Allah bless him and his family and grant them peace) and in the station of ‘Ali (Peace be Upon Him). For it is known that those two—may Allah’s blessings be upon them—have stations and degrees with Allah (Most High) that no one from this Ummah can reach.
And in hadith: it was said, “O Messenger of Allah, what is al-Wasīlah?” He said: “It is the highest degree in Paradise; none attains it except a Prophet, and I hope that I will be he.” And in a narration: “The strike of ‘Ali on the Day of al-Khandaq equals the deeds of my Ummah until the Day of Resurrection,” or as he said—along with other reports besides that.
Therefore, the meaning is that Allah (Most High) will join the righteous descendants to their righteous parents in the general sense of honor—so He grants them of honor what He does not grant others who are like them in faith and deeds. And that added honor and elevation occurred for them because it is part of the completeness of Allah’s reward and honoring of their parents: the parents deserved reward and daragat (ranks) because of their righteous deeds; and among what they deserved is the honoring of righteous descendants. Thus, what the descendants receive of extra ranks and honors is, in reality, by deed—even if they did not do it themselves: their parents did it. And the reward, in truth, belongs to the parents; and honoring the children is honoring the parents—people recognize this and find it within themselves, without doubt or hesitation.
2- Will a believer from the Prophet’s family (Ahl al-Bayt) reach the Prophet’s (May Allah bless him and his family and grant them peace) rank?
The answer has already been included in the first answer, so there is no need to repeat it. We add here:
We may say that Allah—Exalted is He—has joined the Prophet’s descendants, in this worldly life, to their forefather (May Allah bless him and his family and grant them peace) in honor, elevation, and nobility. So, in this world, they possess the honor, dignity, and lofty standing connected to Prophethood; and Allah has taken from this Ummah a covenant to observe that.
And it is known that whoever observes this rank for the Prophet’s descendants (May Allah bless him and his family and grant them peace) will not reach the level that is due to the Prophet (May Allah bless him and his family and grant them peace). By the same analogy, what they attain of honor in the Hereafter will also be of varying degrees—though honor itself differs in its levels.
3- Which is better: a believer from Ahl al-Bayt, or a believing scholar who strives (mujāhid) from outside Ahl al-Bayt?
The anwer: each has virtue, and the measures of virtue and what follows from it of reward are known only to Allah—Exalted is He.
What seems closer to me is that the striving scholar is better than a believer from Ahl al-Bayt who is neither a scholar nor one who strives:
 Allah—Exalted is He—said: “Allah will raise those of you who believe and those who have been given knowledge in degrees (ranks).” [Al-Mujādilah:11] (Official Qur’an translation referenced; see note below).
 And He—Exalted is He—said: “Say, ˹O Prophet,˺ ‘Are those who know equal to those who do not know?’ Only people of reason take heed.” [Az-Zumar:9] (Official Qur’an translation referenced; see note below).
 And He—Exalted is He—said: “He gives wisdom to whom He wills. And whoever has been given wisdom has certainly been given much good.” [Al-Baqarah:269] And many other verses.
And in the Sunnah there is much—such as his (May Allah bless him and his family and grant them peace) saying: “The superiority of the scholar over the worshipper is like the superiority of the moon on the night of the full moon over the rest of the stars,” and the ḥadīth: “The scholars are the heirs of the Prophets,” and many others.
And among what indicates the nobility of knowledge is what Allah—Exalted is He—mentioned about Mūsā (Moses) (Peace be Upon Him)—despite his being among the messengers of firm resolve—following al-Khiḍr (Peace be Upon Him) in the manner of a servant following one served.
If it is said: “The child is a part of his father, and there is no doubt that a part of the Prophet (May Allah bless him and his family and grant them peace) is superior to one who is not.”
We say: No doubt about that; however, this “being a part” here does not take the ruling of literal/essential “being a part,” because among the offspring are the believing and the immoral and the wrongdoer—whereas in the case of literal/essential “being a part,” infallibility would be established for it.
4- Allah—Exalted is He—said: “And that each person will only have what they endeavoured towards.” [An-Najm:39] This does not contradict His—Exalted is He—saying: “And those who believed and whose descendants followed them in faith—We will join their descendants with them…” [At-Tūr:21] That is because the recompense a legally responsible person deserves as a matter of entitlement is only by deed; and there is nothing to prevent Allah—Exalted is He—from giving him what he deserves by his deeds, and then giving him what he does not deserve—purely as (grace) and (mercy).

Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.3