Aaron was the brother of Moses. He symbolizes two things, at different stages of the story.

During the first part of the exodus, when he was Moses' spokesperson, Moses represents the Word as it truly is, as it is understood in heaven, while Aaron represents the Word in its external sense, as it is understood by people in the world. This is why Aaron talks for Moses, and the Lord says of him "he shall be as a mouth for you, and you shall be to him as God." (Exodus 4:16)

Later, after the Tabernacle was built and he was inaugurated as high priest (see Leviticus 8,9), Aaron represents the Lord as to the Divine Good, and Moses represents the Lord as to the Divine Truth.

In Exodus 28:1, Aaron signifies the conjunction of Divine Good with Divine Truth in the Divine Human of the Lord. (Arcana Coelestia 9806, 9936)

In Exodus 32:1, Aaron represents the external of the Word, of the church, and of worship, separate from the internal. (Arcana Coelestia 10397)

In Exodus 4:14, before he was initiated into the priesthood, Aaron represents the doctrine of good and truth. (Arcana Coelestia 6998)

3815. 'And Laban said to Jacob, Because you are my brother' means, because they are kindred, by virtue of good. This is clear from the representation of 'Laban' as a parallel good that springs from a common stock, and from the representation of 'Jacob' as the good of the natural, both dealt with above; and from the meaning of 'brother' as good, dealt with in 3803, in this case that which is kindred since these words are spoken by Laban to Jacob, and therefore by good to good. Furthermore every kinship has its origin in good, for good is related to love. It is the nearest degree of love in the line of descent that is called kindred, and is meant in the proper sense by 'brother'. In the spiritual world or in heaven no other kinships or relationships by marriage exist except those of love to the Lord and of love towards the neighbour, or what amounts to the same, those of good. This has been made clear to me by the fact that all the communities that constitute heaven, and that are countless, are quite distinct and separate from one another according to degrees and differences of love and of faith deriving from this, see 685, 917, 2739, 3612.

[2] This has also been made clear to me by the fact that in heaven they do not acknowledge one another because of any family relationship that had been theirs during their lifetime but solely on the basis of good and attendant truth. A father does not acknowledge a son or daughter, a brother does not acknowledge a brother or sister, and even a husband does not acknowledge his wife, unless they have been governed by similar good. They do, it is true, meet when they first enter the next life, but they part company after that; for good itself - that is, love and charity - determines whichever community a person is sent to. Kinship begins in the community in which each person belongs and spreads from there into all places round about.