I understand that there's a concept of גר כקטן שנולד דמי (not sure I got the words 100% right) - that a convert (ger) to Judaism is halachically considered to have no family.
If that is the case, then would a non-Jew brother and sister who convert be able to marry each other? After all, shouldn't they be considered strangers by the above principle?
And if not, why?