I had a hand come up last night, don't really remember the specifics, but at the end I had the A high flush(beat his high), and used A-5 for my low. The other kid in the hand had A-2 for his low but there was already a 2 on the board.

After I was taking in the chips, him and the rest of the table said that we should split it because his A-2 is lower than my A-5. I said that since there was a 2 on the board his 2 cancelled out and that he didn't have a low hand, therefore I scoop. They didn't want to budge so I just let them split it because it was just a friendly home game. I just want to know who was right for future reference, me or him?

It may depend on what other cards were on the board. If there was three other low cards on the board besides the 2, then he may have had low...But if there were only three cards in total on the board that were low, then his 2 would not play and his next lowest card would....Anyway, we'd need more information.

Like I said I can't really remember the specifics but there were 4 low cards on the board and I think his only other lowcard was a 6. I think the board was something like

2-4-6-7-k

on that board, the nut low would be A-3, 2nd nut would be A-5, 3rd nut would be 3-5.

So is it safe to say that if one of your hole low cards pairs with a board low card it is not playable? ie a-2-k-j would not play on a 2-3-6-7-9 board?

sure it is. i'll play bottom pair with A kicker any day of the week.

2-3-6-7-9 board, in actuality your low w/ A-2 is 7-6-3-2-A.

but with that 2 someone holding 5-4 just made a low of 6-5-4-3-2.

so now you have to play the rag low (the one with the 7) while a total crap low just took your half of the pot.

5 cards w/o pairing.

as long as there's no 5 on the board as well, the pot is yours

Exactly,
the 5 lowest cards w/o pairing. takes the pot.
But being a home game, it's all for "fun" anyway. it's not like you're paying your mortgage with the home game winnings anyway. as long as everyone is having fun, that's what matters.
I never took my home game very seriously. Sure I'm competative and want to win everyones money and show them who the best is, but there are times I love watching the expressions on their faces and agonizing over a call that makes losing a hand very enjoyable too. I like screwing with their heads.