There is some Intergeneric hybridization done with the hardy hibiscus, but sadly, when I've grown the resultant plants, they failed to produce seed...
They had to be vegetatively propagated.
Whether your plants can be crossed... is one of those things where... you learn by doing.
we can't advise, when we don't even know what types of hibiscus are being discussed.
Before attempting Intergeneric crosses, suggest simply growing out the seeds that these produce...