Although gennao can technically mean "begotten," the weight of Scripture is heavily on it meaning "born" rather than "begotten," even in scriptural areas far removed from the John 3 controversy.
In I Peter 1:23, the phrase "having been born again" is anagennao, which comes from gennao, and means "to beget or (by extension) bear (again)." The apostle makes quite clear in I Peter 2:1-2 that he considers those he is writing to as already born, rather than unborn and within a womb. Only a child already born would feed on milk, or Peter's metaphor would be totally wrong.
A similar circumstance appears in Hebrews 5:13-14:
For everyone who partakes only of milk is unskilled in the word of righteousness, for he is a babe. But solid food belongs to those who are of full age, that is, those who by reason of use have their senses exercised to discern both good and evil.
Again, the metaphor pictures an already-born child who eats and drinks.
Paul castigates the members of the Corinthian congregation because of their spiritual immaturity, describing them as babies who needed milk:
And I, brethren, could not speak to you as to spiritual people but as to carnal, as to babes in Christ. I fed you with milk and not solid food; for until now you were not able to receive it, and even now you are still not able. (I Corinthians 3:1-2)
The metaphor of eating and drinking only works if we are considered already born spiritually. We were spiritually begotten by the Father at some point in the past through His calling, but we have progressed beyond that begettal to a spiritual birth long before the resurrection of the dead. There is not a single verse that shows us to be begotten but not yet born.
The analogy of being begotten and in the womb of the church is not only scripturally wrong, it is totally inadequate when God commands us to do practical activities normal to Christian life. A child in a womb cannot pray, study, fast, serve, consider, choose, sacrifice, humble himself, repent, forgive, be merciful, walk in the Spirit, rejoice, love, use wisdom, be discreet, intercede, or bring glory to God.
John W. Ritenbaugh
Born Again or Begotten? (Part Three)
Other Forerunner Commentary entries containing 1 Peter 2:3: