There is no obligation for them to convert but if they can handle it they will get a better place in Olam HaBa. Those who already identify a Jews because their fathers are Jewish should especially consider this (and according to Kabbala there is a special inyan to bring back zera Yisrael). There was a non-Jewish woman who periodically asked Rav Ruderman questions about the sheva mitzvot. When he asked her if she had considered converting she said “Rabbi. I have enough trouble with seven. I don’t need 613”.
Converting to Judaism is not for everybody. There’s alot of rules that we are required to keep, and it’s not easy. One should not consider converting to Judaism unless they really think they have what it takes to keep all of the rules all of the time.