1) Inspite of severe medical objection raised by me earlier (Rather I was first person to raise medical objection in your case still I prefer to put legal points from Act) . I feel apart from this there is no text to refer, you can do whatever your conscious permits. I feel if you both are attached you can do , but remeber please don't give birth to child , adopt child some one too may need love , may be decission to adopt child should be fixed and if pregnant by chances then you should terminate pregnacy immedately in interest of child or take necessary steps from first day that she does not become pregnant
2) Consequence of in relative breeding are seen after even 2-3 genration , May be your grand children will be handicap . If you feel we are talking some thing socailly unethical then you visit Dr. and he will take same stand if he has enough wisdom that next generation or 2-3 generation next can have defects
3) And last thing , myself not orthodox today in world man and man marries and women and women marries in some part of world , They have relationship and in some part of world it is legal as per law . Still I put point only one . Don't give birth to natural child , from both of you , adopt some other child if you want child in your family. Don't risk next generation
4) Very bad consequence in history of in family or in relative breeding is given in this article https://en.wikipedia.org/wiki/Charles_II_of_Spain
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For legal purpose I produce Hindu Marriage Act for reference. Not intersted to study this because myslf only thinking of child not about you and your would be wife . I hope query ends here
Hindu Marriage Act 1955
3. Definitions.- In this Act, unless the context otherwise requires,-
(c)"full blood"and "half blood"- two persons are said to be related to each other by full blood when they are descended from a common ancestor by the same wife and by half blood when they are descended from a common ancestor but by different wives;
(d)"uterine blood" - two persons are said to be related to each other by uterine blood when they are descended from a common ancestor but by different husbands. Explanation.- In Clauses (c) and (d) "ancestor" includes the father and "ancestress" the mother;
(f)
(i)"Sapinda relationship" with reference to any person extends as far as the third generation(inclusive) in the line of ascent through the mother, and the fifth (inclusive) in the line of ascent through the father, the line being traced upwards in each case from the person concerned, who is to be counted as the first generation;
(ii) two persons are said to be "sapinda" of each other if one is a lineal ascendant of the other within the limits of sapinda relationship, or if they have a common lineal ascendant who is within the limits of sapinda relationship with reference to each of them;
(g)"degrees of prohibited relationship " - two persons are said to be within the "degrees of prohibited relationship"-
(I) if one is a lineal ascendant of the other; or
(ii) if one was the wife or husband of a lineal ascendant or descendant of the other; or
(iii)if one was the wife of the brother or of the father's or mother's brother or of the grandfather's or grandmother's brother or the other; or
(iv)if the two are brother and sister, uncle and niece, aunt and nephew, or children of brother and sister or of two brothers or of two sisters.
Explanation.- for the purposes of clauses (f) and (g) relationship includes-
(I) relationship by half or uterine blood as well as by full blood;
(ii) illegitimate blood relationship as well as legitimate;
(iii) relationship by adoption as well as by blood; and all terms of relationship in those clauses shall be construed accordingly.
4. Overriding effect of Act.- Save as otherwise expressly provided in this Act.-
(a) any text,rule or interpretation of Hindu Law or any custom or usage as part of that law in force immediately before the commencement of this Act shall cease to have effect with respect to any matter for which provision is made in this Act;
(b) any other law in force immediately before the commencement of this Act shall cease to have effect in so far as it is inconsistent with any of the provisions contained in this Act.
5. Condition for a Hindu Marriage.- A marriage may be solemnized between any two Hindus, if the following conditions are fulfilled, namely:
(iv) the parties are not within the degrees of prohibited relationship unless the custom or usage governing each of them permits of a marriage between the two;
(v) the parties are not sapindas of each other, unless the custom or usage governing each of them permits of a marriage between the two