Aldon Smith's Family To Have Brain Checked For CTE

Aldon Smith's loved ones are searching for answers after the former NFL star's death ... revealing they are sending his brain to Boston to determine whether he suffered from CTE.

Smith's family hired a legal team to help them investigate what may have contributed to his passing at 36 years old ... and that features several steps, including having his brain examined for damage caused by concussions and other trauma.

Smith was found unresponsive in his truck on Saturday after delivering pizzas to the homeless earlier in the day. A cause of death has not been announced.

Pastor Scott Wagers -- who interacted with Smith on Saturday -- told TMZ the NFLer seemed a little tired, but was otherwise gentle and friendly during their time together.

Smith entered the NFL in 2011 as a first-round pick ... and emerged as a dominant defensive force. Unfortunately, his off-field issues overshadowed his success, and he was suspended several times over the course of his career.

Smith's family claims he experienced numerous concussions during his NFL career ... an injury that has been linked to the degenerative brain disease that causes depression, mood swings and more.

It can only be diagnosed after death.