Van Hohenheim ..

Alphonse had never kept any resentment towards his father who had left them when they were young. Alphonse is the kind of person who never kept hatred or anger inside him. To Alphonse, Van Hohenheim is a important person that he trust unlike his older brother Edward who thinks that their life is better off without their dad.


VAN HOHENHEIM TELLS ALPHONSE HIS SECRETS

It took twenty volumes of the manga until Alphonse finally meets his father again after they left them when he was still a toddler. Of course it was an awkward first greeting, but it was Alphonse who took the first step to talk with his dad. Right away, Alphonse told his dad about their plans and how they will defeat the "Homonculus of the Flask", but Van Hohenheim stopped Alphonse and asked him why did Alphonse not consider his father as one of the enemies. It would have been bad if Van Hohenheim is, however, he stopped Alphonse's long pause and told him that it made his dad happy for trusting his old man right away.

What a good boy.. He can even come to trust a lousy father like me.

→ Van Hohenheim, Fullmetal Alchemist volume 20

What I like about the relationship between the two is how Alphonse accepted his dad with no question. You know how it goes right? You can never pick your family, what you have now is something that you must treasure. It's only natural to fight within family members, but of course it is also your job to accept your family or your dad who left you without saying any word about it. Without question, Alphonse knows that his dad loves him and since Alphonse desires for affection, meeting and conversing with his father again is something that Alphonse have been dreaming of for a very long time.