My elder sister marriage is adjusted with my cousin. I like sister of my cousin. Can I marry her after my sister marriage. Is it a sighar marriage?
Definition of nikkah a-Shighar
I think you refer to nikah a-shighar الشِّغَارُ:
Allah's Messenger (ﷺ) forbade Ash-Shighar, which means that somebody marries his daughter to somebody else, and the latter marries his daughter to the former without paying Mahr. (sahih al-Bukhari)
Nikaah al-shighaar refers to when a man gives his daughter, sister or other female relative whose guardian he is in marriage on the basis that the other man will give him a female relative in marriage, or will let his son or nephew marry his daughter, sister or niece, and so on. The marriage contract done on this basis is invalid, whether a mahr is stated or not (Fatwa)
The major issue with this kind of marriage is the condition:
Man A only allows man B to marry his daughter or female relative (he is guardian/waly of) if man B "in exchange" gives him a female relative (he is guardian/waly of) for marriage.
So in this kind of marriage (even if there is a mahr/sadaq defined) the condition gives it a taste as if the real mahr for the first marriage is that man A can marry a relative of man B.
Note that the majority (some details see below) of scholars are in consensus that once there's a predefined mahr this marriage is technically valid. So the major issue with shighar is the absence of a mahr!
Types of shighar marriage
According to this fatwa (unfortunately only in Arabic) in case of a shighar like marriage (man A marries a relative of man B and vice versa, but without making it a condition for any of the marriages to be accepted) with mahr is legal marriage in all madhabs. So the problem in shighar was only the condition that there's no mahr but one could marry such a "marriage in exchange" if mahr was given (to the brides) on both sides!
This fatwa gives three examples of shigaar like marriages:
الأولى : أن يتزوج كلُّ واحدٍ منهما من قريبة الآخر ومن هي تحت ولايته ، دون اشتراط أن يكون زواج أحدهما مبنياً على زواج الآخر ومتوقفاً عليه ، ومع وجود مهر** مقرَّر لكلٍّ منهما** .
Man A marries a relative of man B and man B a relative of man A, without a condition that the any of the marriages is a condition for the other to be accepted by any of the guardians. For each marriage a mahr is predefined.
This type of marriage isn't the prohibited shighar and it's perfectly legal.
الثانية : أن يتم الزواج بشرط أن يزوج كل واحد منهما موليته من الآخر ، مع عدم وجود مهر لهما ، بحيث يكون بُضْعُ كل واحدةٍ منهما فِي مُقابَلة بضْع الأخرَى .
A marriage would be accepted with the condition if each of the man marries one of his relatives to the other, without mahr, so that the mahr of marrying for A is B marrying A's relative.
This is the shighar as described in the hadith and it is prohibited. Hanafi scholars accept this marriage but under the condition that each husband pays a later mahr and this mahr must be equal, as this according their view makes this marriage valid and no more a shighar marriage.
الثالثة : أن يزوج الرجل ابنته أو أخته أو من هي تحت ولايته ، بشرط أن يزوجه الآخر ابنته أو موليته ، لكن مع وجود مهرٍ لكلٍّ منهما ، سواء كان متساوياً أو مختلفاً .
A man A accepts a man B to marry his relative with the condition if man B gives him a relative for marriage , with a mahr which can be equal or not equal.
This situation is a matter of dispute between scholars:
Dhahiri scholars say that the condition makes it clearly a reason to be considered as shighar, some shafi'i and hanbali scholars also follow this opinion.
Maliki scholars call it "face (maybe alike is a better translation here) of shighar وجه الشغار* and say if this marriage has not yet been consummated it should be made invalid by faskh if it was consummated it is considered as a valid marriage, because of the presence of a mahr.
Most scholars agree that this form is a valid marriage because of the existence of a mahr, but it is not a recommended form of marriage.
Is it not a sighar marriage?
To me your situation doesn't appear to have any relation to shighar so far, but you can check it based on the given information from above.
See also this fatwa in Arabic about the definition of shighar marriage.
And this fatwa in Arabic about the marriage in exchange. And this fatwa in Arabic about shighar and how talaq is done in case of shighar. Also take a look at this post.
Yes you can. Be sure. According to ayeh 23 sure nesaa' (آیه 23 سوره نساء)
Prohibited to you [for marriage] are your mothers, your daughters, your sisters, your father's sisters, your mother's sisters, your brother's daughters, your sister's daughters, your [milk] mothers who nursed you, your sisters through nursing, your wives' mothers, and your step-daughters under your guardianship [born] of your wives unto whom you have gone in. But if you have not gone in unto them, there is no sin upon you. And [also prohibited are] the wives of your sons who are from your [own] loins, and that you take [in marriage] two sisters simultaneously, except for what has already occurred. Indeed, Allah is ever Forgiving and Merciful.