The Three Kindred are, in my opinion, the most essential piece of ADF Druidry. Honoring ancestors, spirits of place, and gods and goddesses was an essential part of the Paganism of the Indo-Europeans. Though perhaps the ancient Indo-Europeans did not fit the spirits they encountered into boxes as neat as we do today, they are nonetheless helpful categories to aid our understanding of IE spirituality.
The Gods and Goddesses are considered the most powerful kind of spirits by most Indo-European cultures. Called the Déiwōs, which translates to "Shining Ones" in the reconstructed Proto-Indo-European language (Ár nDraíocht Féin [ADF], 2009, p. 69), the Gods and Goddesses are humanity's allies, and sometimes, friends. Their power is certainly much greater than our own; many Gods are described as having gifts of foresight or magic, and others are said to possess tremendous strength unthinkable to a human. They are also immortal, a class of being that does not have a permanent physical form or experience death in the way that living things with bodies do. Nonetheless, the Gods have chosen to take an interest in humanity, as evidenced by their ongoing interaction with both our Indo-European ancestors and the Pagan community at large today.
At the center of an ADF Druid's relationship to the Gods is the Proto-Indo-European concept of *ghosti, which means "someone with whom one has reciprocal duties of hospitality" (ADF, 2009, p. 21). The idea is that gifts to the Gods and Goddesses of Indo-European pantheons begin a relationship of reciprocity, in which the Gods and Goddesses are then encouraged by the concept of hospitality to bestow gifts and blessings on their worshippers. The nature of this relationship is not exactly tit-for-tat; but instead each member gives according to his or her means. This means that while a Druid may pour out a shot of mid-range alcohol with a prayer to a God or Goddess, that being will reciprocate in a way worth much more than ten minutes and fifteen dollars; because the resources available to that God or Goddess is much greater than the Druid's.
It is also the duty of the Shining Ones to maintain the cosmic order of things. Most Gods and Goddesses have specific parts of human culture or the world at large that they have jurisdiction over or are associated with. For instance, the Norse God Tyr is often looked to in matters of justice, or the Gaulish God Ogmios associated with eloquence and public speaking. In many pantheons and Indo-European myths, the Gods and Goddesses are shown fighting or at war with a more primal kind of spirit, more chaotic and much less favoring towards humanity; in ADF these spirits are usually identified as the Outsiders. The Shining Ones fight or distance themselves from these spirits to maintain the balance of the cosmos.
The Spirits of Nature are perhaps the most diverse, and therefore difficult to classify, of the Kindred. There are spirits of land and place, house spirits, plant and animal spirits, and in some IE cultures, even specific rocks are said to have spirits. These spirits also seem the most ambivalent towards humanity - unlike the Ancestors or Gods, many of these spirits are hostile towards people, and will not seek a relationship (ADF, 2009, p. 42). On the other hand, since these spirits are not as powerful as the Gods, for some it is easier to build a close, friendly relationship with them. Some Germanic peoples, for example, believed that plants had spirits and were useful in healing because of this (Gundarsson, 2007, p. 28).
It is my personal opinion that the hostility of many nature spirits towards humanity may have been overstated or caused by a Christianized population. It is often mentioned in Irish folklore, for example, that offerings were frequently left out for the Fair Folk - and any offerings missed or stopped were met with anger (Evans-Wentz, 2003, p. 291). It seems to likely to me that tales of angry or hostile Nature spirits may largely be a result of offerings, once frequently given by the local people, stopped and the spirits themselves renounced in the name of the new god. In any case, I have found my local nature and house spirits to be receptive to offerings; and though I always extend any overtures with caution, I have yet to experience any negative consequences from attempting friendship with these spirits.
Nature Spirits are the least mobile of the Kindred, though there are a few Icelandic tales of house wights (troublesome or friendly) following a family to their new residence (Gundarsson, 2007). Spirits of my local park, for example, are best honored in their place of residence; it is unlikely that one would be able to reach them in a far-away city. However, I have also found that in many cases, land spirits know and interact with one another; so that if for some reason I wanted to relay a message or feeling to a spirit in my local park, I could address the spirit of the Platte River basin and ask that spirit to pass the message along (though whether it would choose to or not is debatable).
Just as there are many pantheons of Gods and Goddesses and many kinds of Nature Spirits, there are also many kinds of Ancestors. Though all humans who have passed from this life and their mortal bodies are Ancestors, and all are honored when we call on them, there are of course some who are singled out for greater honor and closer relation to Druidry and individuals today.
The first and most obvious are Ancestors of Blood, those whose DNA directly contributed to making us who we are. Contrary to a popular modern belief about the unimportance of "sperm donors" or "egg carriers", the DNA of our family plays a big part in our personalities, character traits, and areas of struggle in our lives. Equally important, however, are Ancestors of Culture - those Ancestors that we choose to honor or take on because of their actions or important contributions to either modern or ancient society as a whole. For instance, though I have no idea if she is an ancestor of blood, I honor the Celtic warrior-woman Boudicca as an ancestor of culture because of her heroism and bravery in a time when women had a great deal less power than today. I also honor the ancestors of my adopted father as ancestors of culture - though they did not contribute to my DNA, I gained them as ancestors when my father took me as his child.
Though we often think of ancestors as far-distant figures of the past, or great Heroes of long ago, it is also important to remember our Ancestors who have only recently passed. One important ancestor to all of ADF Druidry is Isaac Bonewits, who I am sure continues to guide and watch over his organization and its members from the otherworld. Though limited in life, the beliefs of the Indo-Europeans tell us that in death, people gain a degree of might, magic, and foresight that rests somewhere between the Gods and men. Praying and offering to the ancestors is often just as effective as praying to the Gods - perhaps even more so, as the ancestors are kin, who have a vested interest in seeing their relations healthy and happy.
The Three Kindred - Ancestors, Nature Spirits, and Shining Ones - are all equally important to the faith of ADF-style Druidry. Each one of the Kindred brings unique attributes that are helpful to humanity in some way or another, and also helps us to understand the wider world and otherworld in a more complete way.
Ár nDraíocht Féin, (2009). Our Own Druidry. 1st ed. United States: ADF Publishing.
Kvedulf Gundarsson, (2007). Elves, Wights, and Trolls. 1st ed. United States: iUniverse.
W.Y. Evans Wentz, (2003). The Fairy Faith in Celtic Countries: The Classic Study of Leprechauns, Pixies, and Other Fairy Spirits. United States: Citadel.