There's no "right way" to grieve.

Some people just dont cry when they grieve. Some people feel sick, some people sleep, some people go thru an entire case of Kleenex when they grieve.

As long as he isnt using drugs or alcohol or other unhealthy substances/actions to deal with his grief, he's probably going to be ok. If the "not crying" is distressing him, maybe he should see a grief counselor or support group or something like that...or just sit and talk about it with other people who knew the deceased person.