I second Lissa's reply.

Ogham yes, and specifically used to write ancient Irish or Pictish language. I have a set of cards and a book somewhere called the Celtic Tree Alphabet. Each set of lines corresponds to a letter/sound, and each one also stands for a specific tree; birch, oak, ash, etc.
As for what it means...I have no idea since I haven't studied it beyond the basics of what it is and the trees. I suppose you'll have to ask Aya, I agree that the tats are probably his.

He has several Pictish tattoos.