Niall, the information that it is a "he" is contained in "aige". Agam = with me. Agat = with you. Aige = with him. Aici = with her. Againn = with us. Agaibh = with ye (plural you). Acu = with them.
Hope that helps.
Edit: This list may be useful http://www.irishpage.com/quiz/preppron.htm