I differ to both @ Saurabh V.+ @ Bharatkumar, Advocate [SC has even said marriage of a Hindu with his wife's sister's daughter is not invalid in Hindu law Ref.: Ragavendra Rau Vs. Jayaram Rau {(1897) I.L.R. 20 Mad. 283}. Here the case is that of a marriage of a Hindu with his sisters > husbands > sisters > daughter so how it can ever come under prohibited relationship?]
1. Yes, both of you can marry.
2. Both of you donot come under Sapinda - prohibited relationships as per HMA / SMA.
2.1 Make Charts like these in the link and it would be interesting for me to know if your elders can ever make such relationship chart for you and your alleged to be named your niece;
https://www.lawyersclubindia.com/forum/sapindas-24647.asp
3. Impress upon elders of both sides by reciting below text from the passage of “Digest of Hindu Law, Vol. I, page 120” like this J;
“Male should marry a girl, who is non-spinda (with himself). She is called his sapinda who has (particles of) the body (of some ancestor’s), in common (with him). Non-sapinda means not his sapinda. Such a one (he should marry). Sapinda-relationship arises between two people through their being connected by particles of one body. Thus the son stands in sapinda-relationship to his father because of particles of his father's body having entered (his). In like (manner stands the grandson in sapinda relationship) to his paternal grandfather and the rest, because through his father particles of his (grandfather's) body have entered into (his own). Just so is (the son a sapinda-relation), of his mother because particles of his mother's body have entered (into his). Likewise (the grandson stands in sapinda-relationship) to his maternal grandfather and rest through his mother. So also (is the nephew) a sapinda-relation of his maternal aunts and uncles, and the rest, because particles of the same body (the paternal grandfather) have entered into (his and theirs); likewise (does he stand in sapinda -relationship) with paternal uncles and aunts, and the rest. So also the wife and the husband (are sapinda -relations to each other), because they together beget one body (the son). In like manner brothers' wives also are (sapinda -relations to each other), because they produce one body (the son), with those (severally) who have sprung from one body (i.e., because they bring forth sons by their union with the offspring of one person, and thus their husbands father is the common bond which connects them). Therefore one ought to know that wherever the word sapinda is used, there exists (between the persons to whom it is applied) a connection with one body, either immediately or by descent.”
Degree of Prohibited relationship as per the Hindu Marriage Act, 1955
S. 3 (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 " Sapindas" 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;
S. 3 (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 the father’s or mother’s brother or of the grandfather’s or grandmother’s brother of
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 3(f) and 3(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.
Degrees of Prohibited relationship as per the Special Marriage Act, 1954
S. 2 (b):
"Degrees of prohibited relationship" – a man and any of the persons mentioned in Part I of the First Schedule and a woman and any of the persons mentioned in Part II of the said Schedule are within the degrees of prohibited relationship.
Explanation (I) – Relationship includes, --
a. relationship by half or uterine blood as well as by full blood;
b. illegitimate blood relationship as well as legitimate;
c. relationship by adoption as well as by blood;
and all terms of relationship in this Act shall be construed accordingly.
Explanation (II) – "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.
Explanation (III) – "Uterine blood" – two persons are said to be related to each other by uterine blood when they are descended from a common ancestress but by different husbands.
Explanation (IV) – In Explanations II and III, "ancestor" includes the father and "ancestress" the mother;
THE FIRST SCHEDULE [DEGREE OF PROHIBITED RELATIONSHIP]
PART – I
Mother.
Father’s widow (step mother).
Mother’s mother.
Mother’s father’s widow (step grand-mother).
Mother’s mother’s mother.
Mother’s mother’s father’s widow (step great grand-mother).
Mothers’s father’s mother.
Mother’s father’s father’s widow (step great grand-mother).
Father’s mother.
Father’s father’s widow (step grand-mother).
Father’s mother’s mother.
Father’s mother’s father’s widow (step great grand-mother).
Father’s father’s mother.
Father’s father’s father’s widow (step great grand-mother).
Daughter.
Son’s widow.
Daughter’s daughter.
Daughter’s son’s widow.
Son’s daughter.
Son’s son’s widow.
Daughter’s daughter’s daughter.
Daughter’s daughter’s son’s widow.
Daughter’s son’s daughter.
Daughter’s son’s son’s widow.
Son’s daughter’s daughter.
Son’s daughter’s son’s widow.
Son’s son’s daughter.
Son’s son’s son’s widow.
Sister.
Sister’s daughter.
Brother’s daughter.
Mother’s sister.
Father’s sister.
Father’s brother’s daughter.
Father’s sister’s daughter.
Mother’s sister’s daughter.
Mother’s brother’s daughter.
Explanation – For the purposes of this Part, the expression "widow" includes a divorced wife.
PART – II
Father.
Mother’s husband (step-father).
Father’s father.
Father’s mother’s husband (step grand-father).
Father’s father’s father.
Father’s father’s mother’s husband (step great grand-father).
Father’s mother’s father.
Father’s mother’s mother’s husband (step great grand-father).
Mother’s father.
Mother’s mother’s husband (step grand-father).
Mother’s father’s father.
Mother’s father’s mother’s husband (step great grand-father).
Mother’s mother’s father.
Mother’s mother’s mother’s husband (step great grand-father).
Son.
Daughter’s husband.
Son’s son.
Son’s daughter’s husband.
Daughter’s son.
Daughter’s daughter’s husband.
Son’s son’s son.
Son’s son’s daughter’s husband.
Son’s daughter’s son.
Son’s daughter’s daughter’s husband.
Daughter’s son’s son.
Daughter’s son’s daughter’s husband.
Daughter’s daughter’s son.
Daughter’s daughter’s daughter’s husband.
Brother.
Brother’s son.
Sister’s son.
Mother’s brother.
Father’s brother.
Father’s brother’s son.
Father’s sister’s son.
Mother’s sister’s son.
Mother’s brother’s son.
Explanation – For the purposes of this Part, the expression "husband" includes a divorced husband.