Kovac started Bellingham, but changed the former Sunderland midfielder at the break after an ineffective first 45.
Sky Deutschland says Mark Bellingham, who also acts as Jobe's agent, waited for Kovac in the players' tunnel after the 3-3 draw.
Instead, he spoke with BVB chief Sebastian Kehl and was reportedly "emotional" over the decision to hook his son and the team's overall performance. Bellingham Snr also made clear he wanted to speak with Kovac.
Kehl later said: "We are all disappointed about the result yesterday. And still, the active area at our club remains reserved for players, coaches and officials, not families and advisors.
"This will not happen again. We have made this clear to all involved."
Bellingham Snr's presence was also noticed by BVB players, who took note of his "emotional" manner.