But wasn't Banasura a great devotee of Mahadev & Kartikeya? Which is why both of them promised him that they'd support him when he fought a threatening war? Both of them fought on his side against Krishna, Pradhyumna, et al.
The original story that I read was that Banasura used to seranade Mahadev w/ 500 instruments of his 1000 arms, which Mahadev used to enjoy & dance to. As a result, Mahadev gave him the above promise.
After a while, Banasura complained to him that his 1000 arms were useless, & Mahadev cursed him that one that was his equal would humble him. Hence the 'defeat' of Shiva by Krishna, that's sometimes held up to 'prove' the superiority of the latter over the former.
But the WUs I've been reading seem to suggest that everyone in Shiva's family has issues w/ Banasura, which is not how I recall any of it.