ὅσοι δὲ ἔλαβον αὐτὸν, ἔδωκεν αὐτοῖς ἐξουσίαν τέκνα θεοὺ γενέσθαι, τοῖς πιστεύουσιν εἰς τὸ ὄνομα αυτοῦ,οσoι: as-many-as.
ὅσοι δὲ ἔλαβον αὐτὸν is a dependent clause. Every clause has its own subject and verb. What is the subject and verb of this clause?
δε is an adversative conjunction usually translated “but”.
ἔδωκεν αὐτοῖς ἐξουσίαν
εδωκεν is from the verb διδωμι which is one of the –μι verbs; there is no need to learn them at this point (see BBG 34.6 if you like). You should already recognize the augment. Recall that verbs ending in -εν are third singular; verbs ending in -αν are third plural. This makes εδωκεν easy to parse.
τέκνα θεοὺ γενέσθαιWhich of the adjectival questions is this phrase answering?
τοῖς πιστεύουσιν εἰς τὸ ὄνομα αυτοῦ,
If it is articular, then you know it must be either attributive or substantival. An attributive participle is translated just like an attributive adjective; e.g. the running dog, the sweating carpenter.
Remember that even adverbial participles still modify a noun of some sort. In this case, πιστευουσιν is articular, and there is no noun around for it to modify. Hence, it must be substantival. This means it is performing one of the noun functions. You can translate this participle as “believers…” or “to those who believe…” This participle is dative and is in apposition to αυτοις.
Now watch πιστεύουσιν evolve:
πιστεύ- the stem
πιστεύο add the connecting vowel
πιστεύοντ add the participle morpheme
πιστεύουντσι add the case ending
πιστεύουσι the ντ elides (see the footnote in BBG page 248)
πιστεύουσιν movable nu
οἳ οὐκ ἐξ αἱμάτων οὐδὲ ἐκ θελήματος σαρκὸς οὐδὲ ἐκ θελήματος ἀνδρὸς ἀλλ’ ἐκ θεοῦ ἐγεννήθησαν.οι; relative pronoun or article? If it is a relative pronoun, then it is also a DMW. If a DMW, then a dependent clause is also present. If it is a dependent clause, then it must have its own subject and verb. εξ is the preposition εκ but why the changed spelling?
The repetition of ουδε here is translated into English by using a correlative conjunction. neither… nor…
εγεννηθησαν is a regular form. Know its evolution: