No, he isn't. He was implied to be Monet's grandson. When he first appeared, the writing made it seem like Storm would end up with him after she broke up with Forge (and then with Cable after she broke up with him again). The only reason people assume that they're related is because: they're black and because Bishop's grandmother is a black woman with white hair - never mind that plenty of old black ladies got white hair.
And I know, Times and Life of Lucas Bishop hints a bunch of **** but at the end of the day - that miniseries had so many continuity errors that it can't be canon.