Justin Bieber's blood father is back on the scene ... just days after some huge events in his son's life, and word he had been leaning on Pastor Carl Lentz for fatherly guidance.

Bieber's pops, Jeremy, flew to L.A. from Ontario, Canada over the weekend with Justin's younger brother, Jaxon, in tow. Jeremy was seen driving around town in a convertible ... tailing Justin who was in his own vehicle.

Sources connected to Bieber say Jeremy's visit is absolutely a direct response to Justin's tumultuous week -- from pulling the plug on the Purpose tour, to accidentally hitting a pap with his truck.

And there's this -- as we first reported, Lentz has stepped up over the last several months as a father figure ... spending time with Justin on the road, and back home in Los Angeles. He's the one Justin turned to when he wanted to discuss ending the tour.

Our sources say Justin's had little, if any, relationship with Jeremy all year. It appears the last time they were together was around Christmastime. We're told Jeremy's here now because he just wanted to reconnect and hang with his kid.

So far, so good. Justin's been pretty chill during the visit.