marriage help

boy will complete 21 years in Nov 2018 and girl completed 27years in Jan 2018 they both love each other they decided to marry in Jan 2019, but girl family not agree for marriage bcoz caste issue and age issue and boy family not agree bcoz girl family not agree for marriage, boy family will agree when girl's family will agree but they are not agree, so how they will marry and where please suggest and which documents will require, they live in Mumbai can they marry in Arya samaj Mandir after November 2018 when boy completed 21 years