So I have two male Syrian hamsters father and son they have been together since birth and ever since my hamsters mom passed away he started to become closed off but when I separated them from the cage he lived in where he grew up with his dad he just shut down and would not eat as often ,exercise or let me near him even though previously he was quite tame but after a few months I saw how scared and unhappy he was and tried to reintroduce them he instantly went to his dad and they both got together well even after I kept him there for a week I saw him eat with his dad more often and also exercise in his wheel so I decided to keep them together since he seems to do way better with his dad than alone so is this still a good idea ?
no it is no where near animal cruelty
Animal cruelty is the act of harming or unjust treatment of animals under care.
your hamster was grieving badly. he was probably close with his mother I suggest getting a female hamster for him someone he could bind too however I think you do not know what a Syrian hamster is
A Syrian Hamster is primarily SOLITARY meaning they prefer to be isolated from other Syrian hamsters just because they seem to live in coexistence does not mean a fight will not occur. if you get a female Syrian hamster know they are aggressive to males (when not in heat) and at best Tolerate them. at a young age Syrian hamsters can be kept together but once they get of a bigger size(unweaned from the mother) its best to separate them.
Syrian hamsters are territorial. but they can be equally affectionate. they will form bonds at times. with individuals although they are perfectly content wih being solitary. hence if the hamster was mourning more than likely it formed a rather strong bond with the mother.