The sister of your grandmother is your great aunt
The daughter of your great aunt is your parent's first cousin and your first cousin, once removed. Her husband is not related to you.
A few people might try to call him your first cousin, once removed-in-law but most would find that uselessly complex and would call him, "the husband of my first cousin once removed," or "my cousin's husband."
In biological terms you are not connected at all, except for the obvious fact that you are both humans. Apart from that, you are not relatives of any kind.
AnswerYour great aunt is either the sister of your grandparent or the wife of the brother of your grandparent.
If she is the sister of your grandparent, then her husband, his brother and the brother's daughter are not related to you.
If she is the wife of the brother of your grandparent, then her husband's brother is your grandfather (and the daughter is your mother or your aunt) or the husbands brother is another of your great uncles (and the daughter is your first cousin, once removed).
You are a second cousin to your grandmother's sister's daughter, so you are second cousin, once removed to her son.
If your great great grandmothers were sisters, your common ancestors are your great great great grandparents. That makes you 4th cousins.
If you have no siblings but your daughter has an uncle, he is the brother of your spouse, your brother-in-law.
Your grandmother's sisters are your Great Aunts.
Daughters of one (or both) the same parents are either sisters or half sisters.
Yes, along with your grandfathers' sisters, if any.
Some nieces of sisters are related to each other and some are not. Your niece is the daughter of your brother or sister (your siblings). If you have more than two siblings and at least two of them have daughters, those daughters are your nieces and they are first cousins to each other. You can also have a niece who is the daughter of a sibling of your spouse. If two sisters have nieces who are daughters of their spouse's siblings, those nieces are not related to each other (unless the spouses are related to each other, as when two brothers marry two sisters)
Brother-in-law
Most likely they would not be related to you
Your mother's sister-in-law is either the wife of her brother (your uncle), or your father's sister (your aunt). The niece of your uncle's wife is not related to you, unless she is you, your sister, or a girl cousin who is the daughter of another of your mother's brothers or sisters. The niece of your father's sister is you, your sister, or the daughter of another of your father's brother's or sisters. If your father's sister is married, she may have nieces who are the daughters of her husband's brothers or sisters. Those nieces are not related to you.
third cousins
Your brother's father-in-law is not related to you unless you and your brother married sisters from the same family. Then he would be your father-in-law, too.
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