"He is the oldest and the firstborn, the Fatherless and childless.
He was there before the elves and is there still."

OK.

Being the 'Oldest' means that he must have begun sometime, unlike Eru who had been arounf forever.

Being 'Firstborn' means that he was actually concieved, in this case in the mind of Iluvatar.

Being 'fatherless'...well you have to look at who said it (Goldberry I believe). Goldberry had a mother, and therefore (although never mentioned) that seems to indicate a father as well (maybe Ulmo - who knows). But anyhow the point being she had at least one parent. When she said this she was looking at it with her own experiences in mind (who can do any more than that). Therefore she used a term which fit Tom B. Also with her being his wife, she would be well aware that he was childless, so thats simple enough.

Being around 'before the elves...' simply means he existed and was wandering the lands before the elves existed. But then so were all the other Valar and Maiar, so he is not that special in that regard.

Tolkien had many enquiries about Tom from people probing for answers and although there has been much speculation on what he really is Tolkien was adamant that he was an enigma and did not need explaining because he thought there should be some mystery in every fairy-tale. Some have attempted to explain what he was and where he came from, but none of these explanations hold much water, for they rely on ideas and suppositions that Tolkien makes no links to and does not allude to at all.

The easilest and most logical way is to think of Tom as a Maiar. A very powerful independant one, but a Maiar none-the-less.

Cheers

Padster