DMX Welcomes Baby #15

DMX has a challenge most parents would find daunting ... remembering the names of all of his kids, which now number 15.

The baker's dozen plus 2 was born Friday in NYC ... weighing in at 6 lbs, 10 oz.

His name -- Exodus Simmons. The mom is X's longtime GF, Desiree. It's her first child.

The rapper missed the delivery -- he was in Arizona when Exodus popped out. But he flew to NYC for the baby's first night in the world.

X tells us he's overjoyed, calling the baby a "blessing."

Lots of blessings.