Jeevs is Kaal and Rageshwari's son and Rani is Rana Ji & Gyatri's daughter..so they both have 2 different set of parents thus they're not related or step siblings either...whether Rageshwari was married to Rana Ji or not, is not a factor...they're not in any way related by blood...so no step sibling issues either...they can easily get married.
FYI if anyone isn't aware, Lovely aka Bindu is Swarnalekha and Lakhan's daughter apparently.