Sometimes with babies, the more sleep they have the more they want. You could start by bringing bedtime forward and ensure he does to bed at between 7 and 7.30. At least THAT way if he wakes early, he should have had enough sleep to make him happier.
However, I have a rule (cruel mother than I am) that my day does NOT start before 7am (!!!) and so when my babies were small and if they started early waking, I would try going in, settling, and leaving again as if it were the middle of the night (feeding, quick cuddle, pickup/put down method, whatever worked best for me with each child at the time). No talking. No lights, VERY boring mummy. If crying was persistent, sometimes I would sit in the room, sometimes holding, sometimes not, being VERY quiet, again, no talking, no lights etc etc until that magic 7am moment came and then we could do "Good Morning, switch on lights etc. After a short time, it seemed to sink in that it was pointless excercise waking before 7am, as there was nothing to get up for. I am pretty certain it was a MN tip from someone that sent me down this route.
Sounds simple, but it worked, AND (BTW) esp. with DD2 who was waking at 5 - 5.30 every morning for a short while.
Otherwise, you may end up "training" them that 5am is a perfectly normal time to start the day, and THAT is what becomes habitual. (certainly was with a friend of mine whose 2.5 yr old STILL wakes at 5am every day now...
AND my sister used to think 5.30am was a normal start to the day with babies and it was only months after that she realised that an hour or so after getting up, her DS was consistently going back to sleep for a couple of hours, but by this time, she was already up!