You address that your daughter and son-in-law are cheap by not saying anything. Whether they are cheap or profligate is for them to be as a part of their personalities. If they are old enough to be married they are no longer little enough for you to try to mold them.
No, your son-in-law is married to your daughter and his brother is not your son-in-law, but simply your son-in-law's brother or your daughter's brother-in-law.
A son's wife is called your daughter-in-law.
If your daughter's brother-in-law is the brother of your son-in-law he is not otherwise related to you.If your daughter's brother-in-law is husband of her sister, then he is your son-in-law.
Daughter is the opposite of son.
In English there are no masculine or feminine forms. English uses gender specific nouns for male or female.The gender specific noun for the husband of your daughter is son-in-law.The gender specific noun for the wife of your son is daughter-in-law.
Your son-in-law's brother's son is not related to you, but is your daughter's nephew.
Your son-in-law is your daughter's husband.
Your daughter-in-law's sister is not related to you, but is your son's sister-in-law.
There is no time limit on a son-in-law. Your son-in-law is the husband of your daughter and remains so unless and until your daughter is no longer married to him.
yes
The brother of a daughter in law is the son in law.
daughter...daughter in law.