Is it permissible to associate with someone despite their abundant sins and repeated relapses after repentance, and the feeling of unworthiness?

You must initiate a sincere repentance by abandoning the sin, regretting it, and resolving never to return to it, while concealing it and not informing anyone about what happened. If you sincerely repent, then there is no blame upon you for marrying the person you wish, for true repentance erases what came before it. Whoever repents, Allah accepts his repentance, and one who repents from a sin is like one who has no sin. You can benefit from the aforementioned person if he is a man of knowledge, piety, and good character.