The singer-songwriter hopped on the phone for an interview with "John and Tammy: San Diego's Morning Show" recently ... and, he talked about the now-defunct band including his feelings toward his ex-bandmate.

BK says he's grateful for all the fans who support the group and their individual endeavors post-split before dropping a bombshell ... namely, he never wanted FGL to come to an end.

He explains, when conversations about individual routes started happening with TH, he wanted to both stay together while simultaneously putting out solo work -- intertwining them somehow.

Kelley admits he has no idea how such a move might work in practice, but he reveals he couldn't get on the same page with Tyler about it ... so, they decided to move out of the Southeast.

Despite the breakup, Brian makes it clear he holds no ill will toward Tyler ... adding he's always rooting for him -- and, leaving the door open for a future reunion.

So, no acrimony here ... not exactly surprising given how the guys left things publicly. Remember, they ended their last performance with a goodbye to fans before hugging and walking off different sides of the stage -- a symbolic close on the chapter in their music lives.

BTW ... each guy's released a couple solo albums in the last few years -- including Hubbard's "Strong" in April and Kelley's "Tennessee Truth" earlier this month.