Your ancestors are the people whose children lead eventually to you. They are your mother and father, grandmothers and grandfathers, great grandparents, great great grandparents, etc.
Your cousins are the children, grandchildren, great grandchildren, etc, of the brothers and sisters of your ancestors.
== == When people talk about their cousins, 'removed' is a reference to the difference in generations. Your mother's cousin would be your cousin once-removed. The children of your mother's cousin would be your second cousins, the same generation of descendants from the common ancestors. Most people just refer to them as cousins and don't worry about the specific generation. The genealogists in the family like to be more specific.
A niece is the daughter of your brother or sister. A cousin is the son or daughter of your parent's sister or brother.
The terms 'great cousin' and 'grand cousin' are not ones used in genealogy. Your family may use the term, but it is not in common usage and has no standard meaning.
They would be second cousins, once removed. The descent is from a common ancestor. Thus 1st cousins share a grandparent as a common ancestor. 2nd cousins share a great-grandparent as an ancestor. If the descent from the common ancestor is not an equal number of generations, the inequality is expressed as 'removed' from the oldest generation being compared.
Your "cousin's neice by marriage" could be the daughter of your cousin's spouse's brother or sister, or the wife of your cousin's brother or sister's son, or even the wife of the son of your cousin's spouse's brother or sister. Obviously under the right circumstances your cousin's niece by marriage might actually be the same person as your granddaughter.
Your first cousin's son is our first cousin, once removed. Your child and that person are second cousins The "number" of the cousin is the smallest count of intermediaries back to the common ancestor (Don't count the common ancestor) then the "removed" number is the difference between the counts
If your uncle's cousin is also the cousin of your parents, you are first cousins once removed. If not, there is no relationship as you do not share a common ancestor.
It will depend on whether or not you share a common ancestor. They could also be second cousins, if you all share a Great Grandparent. If you do not share a common ancestor, there is no relationship between you.
ancestors are dead
Not unless you share a common ancestor.
It depends on if you share a common ancestor. If not, there is no relationship.
you anwser
A relative refers to any person related to you by blood or marriage, such as parents, siblings, aunts, uncles, cousins, etc. An ancestor specifically refers to someone who is part of your direct line of descent, like your grandparents, great-grandparents, etc. In other words, all ancestors are relatives, but not all relatives are ancestors.
That will depend on whether you share an ancestor. If there is no common ancestor, there is no problem. If there is, the laws of your jurisdiction will apply.
There is no relationship between the two of you. You do not share a common ancestor. To your husband he would be a second cousin once removed. Most families would refer to them just as a distant cousin.
They are your cousin. Nothing changes sharing a common ancestor.
You could easily be unrelated to your grandfather's cousin's second cousin.If the two of you are descended from a common ancestor, the closest relationship possible between the two of you is second cousin, twice removed.If your grandfather's cousin is not his first cousin, then the relationship is more distant.